Title of Invention	"A NITRIDE GLASS HAVING GENERAL FORMULA axByYz AND THE METHOD FOR PREPARING SAID NITRIDE GLASS"
Abstract	A nitride glass having high refractivity index and good hardness values with the general formula αxßyγz wherein a is at least one electropositive element chosen from the group of alkali metals Na, K and Rb, alkaline earth metals Be, Mg, Ca, Sr and Ba, transition metals Zr, Hf Nb, Ta, W, Mo, Cr, Fe, Co, Ni, Zn, Sc, Y, Mn and La, main group elements Pb, Bi, and f elements Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu, Th, Pa and U; (3 comprises Si and optionally at least one of the elements of the group of B, Gel Ga and Al; and γ is N or N together with O2whereby the atomic ratio of O:N is in the interval from 65:35 to 0:100, wherein the ratio α:ß is in the interval from 30:70 to 60:40, preferably in the interval from 41:59 to 60:40, wherein the ratio ß:γ is in the interval from 33:67 to 22:78.

Title of Invention

"A NITRIDE GLASS HAVING GENERAL FORMULA axByYz AND THE METHOD FOR PREPARING SAID NITRIDE GLASS"

Abstract

A nitride glass having high refractivity index and good hardness values with the general formula αxßyγz wherein a is at least one electropositive element chosen from the group of alkali metals Na, K and Rb, alkaline earth metals Be, Mg, Ca, Sr and Ba, transition metals Zr, Hf Nb, Ta, W, Mo, Cr, Fe, Co, Ni, Zn, Sc, Y, Mn and La, main group elements Pb, Bi, and f elements Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu, Th, Pa and U; (3 comprises Si and optionally at least one of the elements of the group of B, Gel Ga and Al; and γ is N or N together with O2whereby the atomic ratio of O:N is in the interval from 65:35 to 0:100, wherein the ratio α:ß is in the interval from 30:70 to 60:40, preferably in the interval from 41:59 to 60:40, wherein the ratio ß:γ is in the interval from 33:67 to 22:78.

Full Text	Technical field The invention relates to a nitride glass, a method for preparing a nitride glass and the use of the glass. Technical background Silicon nitride and sialon based materials are recognised as ceramics in high temperature engineering applications due to their high chemical and thermal stability combined with superior mechanical properties. In these systems, self-diffusion processes are relatively slow and they may require an oxide-sintering additive to provide conditions for liquid phase sintering. During sintering, the additive reacts with silica on the surface of the silicon nitride particles and some of the nitride forms an oxynitride liquid, which is converted into a glass phase during cooling. The composition and volume fraction of such oxynitride glass phases strongly influence the properties of the materials. The glass forming regions have been investigated by many different researchers. The existence of sialon glass was first reported by K. H. Jack, J. Mat. Sci. Rev. 11 (1976) 1135-1158. T. H. Elmer, and M. E. Nordberg, J.Amer. Cer. Soc. 50 (1967) 275-279, introduced nitrogen into a high silica glass by heating the melt in NH3 atmosphere. H, 0. Mulfinger, J. Amer. Cer. Soc. 49 (1966) 462-467 produced nitrogen containing soda-lime glass by adding 81^4 to the synthesis mixture. The effect of nitrogen concentration in silica glass on the hardness properties was studied by Shillito et al, Cer. Soc. 63 (1978) 537. It was suggested mat the incorporation of N2 into a silica glass affects the material properties due to the difference in the bonding strength of Si-N compared to Si-0. By comparing Y-sialon glasses with SiO2-Y203~Al203 glasses an increase in hardness could be pointed out by introducing nitrogen in the silica glass, where oxygen atoms are partly replaced by N". me naroness 01 tne glasses was increased wiin an increase of nitrogen content, R. E. Loehman, J. Non-Crys. Solids 56 (1983) 123-134 disclosed that mixtures of oxides and nitrides could be melted and quenched to form glass. By introducing nitrogen into the oxosilicate glass, several material properties were improved, such as increase in the glass transition temperature, hardness, fracture toughness, elastic modulus and chemical durability. The dissolution of nitrogen in oxosilicate melts was further studied by E, A. Dancy andD. Janssen, Canadiaa Metallurgical Quarter 15[2] (1976) 103-110, who reacted CaO-Al203-SiO2 at 1550°C in 1 atm. N2 gas. The amount of 0,25 to 2,5 wt% nitrogen could be incorporated by this technique while as high as 4 wt% nitrogen was incorporated by dissolving solid Si3N4 in the melt. The nitrogen concentration in the melt is probably due to the strong and much favourable triple bond in the N2 molecule. Jack et al. disclosed bulk samples of oxynitride glass obtained by pressure-less heat treatment of a mixture of 14Y2O3-59Si02-27AlN hi a boron nitride crucible at 1700PC in nitrogen atmosphere. This sample was found to have a refractive index of 1,76 and a nitrogen concentration of 9 at% corresponding to an O:N ratio of 86:14. Silicate glass is usually made from oxosilicates. The highest possible condensation degree in pure oxosilicates is found for Si02,wherein every oxygen atom is coordinated by two silicon atoms. It is possible to form glass from pure Si02- This form of glass has been found to have many superior physical properties, such as a high melting point, good mechanical properties and transparency for UV photons. However, a high synthesis temperature is needed for the fonnation of SiO2 glass. Glass modifiers such as Ha, K+ and Ba2+ are added to SiO2 in different concentrations in order to lower the melting temperatures and the manufacturing cost. By introducing! glass modifiers, the network structure of SiO2 is partially broken and some of the oxygen atoms are therefore connected only to one silicon atom. Oxygen atoms connected to only one silicon atom are called apex atoms and oxygen atoms connected to two silicon atoms are named bridging atoms. The three dimensional Si-0 network in the glass can be maintained when only one out of four oxygen atoms of the Si04 tetrahedra are apex. At least three oxygen atoms must be bridging between two silicon atoms to get a three dimensional network. This restriction of the condensation degree makes it possible to form oxosilicate glass only in the composition range Si02 -MxSiO2,5. The highest concentration of the The concept of introducing nitrogen into the glass chemistry has previously been lused in sialon glasses. By quenching melts of M-Si-Al-O-N from high temperatures, glass phases of sialons with glass modifiers such, as La3 and Y34" were obtained. The composition limit concerning Ln (lanthanide) content, which were used as the glaiss modifiers, and nitrogen content was reached with the composition LasSijoAljOj-^Ns, described by N. K. Schneider, H. Lemercier and S. Hampshire, Materials Science! Forum, 325-326 (2000) 265-270. This composition gives the highest lanthanum and nitrogen content ever obtained in a nitride based glass at ambient pressure. The cationic composition given in atomic percent is then La; 25%, Si: 50% and Al: 25% and the anionic composition given in the same way is O : 84,2% and N: 15,8%. The synthesis technique used for preparation of such glasses has limited the nitrogen content as well as the glass modifier content (lanthanum in the example mentioned above). Accordingly, the glass materials that are present today have a nitrogen content corresponding to the 0:N ratio of 84,2:15,8. However, since demands for new glass materials having higher strength and improved physical properties in other respects, not least for various optical, ceramical and coathag-technological applications, continuously are raised, it would be a great advantage to provide new materials witji even better properties. ! One oxonitride glass with higher lanthanum and nitrogen content has been disclosed by A. Makishima, M. Mitomo, H. Tanaka, N. li and M. Tsutsumi, Yogyo-Kyokai-Shi 88[11] (1980) 701, possible to synthesis only at high nitrogen pressure (30 atm.)- the composition of this glass have been reported as La^Sizo.oC^xsNu^ corresponding to a La;Si ratio of 49:51 and an O:N ratio of 70:30. W. Schnick et al. Chem., 9 (1999) 289 introduced a route for introducing nitrogen Into the silicate chemistry other than the obvious reaction of the silicate melt with NI gas for synthesis of crystalline nitridosilicates, oxonitridosilicates and oxonitridoalumiiiosilicates, i.e. not glass material^ by using electropositive metals; together with silicon diimide (SiCNH)2) in a radio frequency furnace. The above i mentioned synthesis route was accordingly used only for producing crystalline phajses. The glass materials described above have certain limitations in chemical composition regarding both nitrogen content as well as concentration of glass modifiers. The chemical composition of such material is a crucial parameter defining the physical properties and for that reason also different possibilities in applications. A problem with nitrogen containing glass today is that there are requirements for qven better physical properties of glass than is known today. There are no known methods for increasing the nitrogen content' of the glass and thereby try to improve its i properties. The method of Makishiina et al has yielded the highest known nitrogen-content, but that method has the disadvantage of requiring complicated equipment and is expensiv Summary of tfae invention It is the purpose of the present invention to provide a new glass material, and a method for its manufacturing, thereby solving the problems posed above and meeting the demands on this point The present invention is directed to overcoming the problems set forth above. This is achieved by producing nitride glass using electropositive elements in their metallic state, as nitrides or any other compound that would transform into metallic state or a nitride when heated in nitrogen atmosphere preferably together with silicon nitride and silicon oxide. In a first aspect, the present invention relates to a nitride glass. The new glass material shows clearly surprising and excellent properties such as extremely high refractiviity index and very good hardness values. In a second aspect, the present invention relates to a method for preparing a nitride glass, without using high nitrogen pressure during the synthesis. A manufacturing method for nitride glasses is provided, wherein the nitrogen content is possible toi be increased, compared to known glass material manufacturing methods. The atomic ratio of O:N is in the interval from 65:35 to 0;100. In a third aspect the present invention relates to the use of a nitride glass in several different applications, e.g. in a surface coating for providing an improvement of mechanical properties on an object such as eye-glasses; in watches and as glaze on different ceramics; in synthetic gemstones; in fibre optics and other optical data i transfer components; in an optical device, such as an optical lens; in a sintering ! additive for ceramic sintering; in bio-ceramics, such as an implant; in a magneto-optical device, wherein the glass modifier is at least one magnetic element such a\|s Dy, Nd, Sm, Tb or Pr as well as a component in a CD and/or a DVD device. Thus, due to the high nitrogen content of the glasses of the invention, unique features of improved mechanical properties are provided, such as a high hardness value, a high melting point, and improved physical properties such as a high refractivity index. Further, strong paramagnetic glasses can be obtained by using magnetic f-elements as glass modifiers, whereby high concentrations of the magnetic ions can be obtained; Detailed description of the invention In the first aspect, the present invention relates to a nitride glass with the general formula o^py^, wherein a is a at least one electropositive element chosen from the group of alkali metals Na, K and Kb, alkaline earth metals Be, Mg, Ca, Sr and Ba, transition metals Zi, Hf, Nb, Ta, W, Mo, Cr, Fe, Co, Ni, Zn, Sc, Y, and La, main group elements Pb, Bi, and f elements Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Pa and U; P is chosen from the group of Si, B, Ge, Ga and Al; and Y is N or N together with O, whereby the nitrogen content given as atomic ratio of O:N is higher than 65:3 5. The atomic ratio of O:N is preferably higher than 65:35, more preferably higher than 41:59 and most preferably higher than 20:80. A preferred embodiment is when a is La and (5 comprises Si and the atomic ratio of 0:N is in the interval from 65:35 to 0:100. In a second aspect, the present invention relates to a method for preparing such a nitride glass comprising the steps of a) mixing chemicals corresponding to the desired composition by using a as a pure metal and/or the corresponding metal nitrides or metal hydrides or any other compound that transforms to the corresponding nitride in nitrogen atmosphere during the synthesis; b) heating said compounds to at least 1000 °C in the presence of nitrogen gas, thereby obtaining a melt; c) maintaining the temperature of step b) until the mixed chemical compounds have formed a homogenous melt; and d) cooling the melt to a temperature below the glass transition temperature and usitig a cooling rate, that is sufficient in order to obtain a glass phase. The nitrogen gas is present as long as the sample has a temperature higher than 1000°C in order to avoid dissociation or oxidation of the glass sample. The heating in step' b, is obtained during 1 second to 60 hours. The temperature in step c, is maintained until equilibrium is reached, preferably diiuring 4 to 24 hours. The time will depend on various parameters, such as the furnace used in the process and the sample composition. The synthesis temperature, or melting temperature, of step b and c is preferably above 1500°C and more preferably above 1800°C, depending on the composition of the melt. Even higher temperatures could be used Standard furnaces could be used in the method for preparing a nitride glass according to the present invention. However, it is important, that the furnace can operate at the temperatures from room temperature to 2000°C. In the examples presented below: a graphite furnace was used. Other furnaces which one could achieve equally high temperatures, with the possibility of quenching the samples, in nitrogen atmosphere can also be used. The skilled person would know what type of crucible material to choose since the temperature of the melt can be above 1500°C. The material used in the crucible should be inert to the melt at temperatures at least above the synthesis temperature used j depending on the glass. Thus, the compounds used in the method should be place boron nitride. These materials are possible to use due to their high melting points as i well as being rather inert to the melted samples formed in the synthesis route. So far the inventor has tried niobium, tungsten, molybdenum and tantalum as well as boron nitride. In the case of BN a small reaction could be observed between the melt and tije crucible. This shows at the same time that BN can be introduced in the nitride based glass. ; New nitride glasses can by using this new synthesis approach be produced with a large variety of chemical compositions, a is the glass modifier, or the element that is not ] involved in the network structure, p is the cation that together with the anion y form \ the network structure. The ratio a:p is in the interval from 30:70 to 60:40, preferably 51:49 to 60:40, depending upon the composition. The ratio P:y is in the interval fronji 33:61 to 22:88. The atomic ratio of 0:N is in the interval from 84:16 to 0:100, preferably in the interval from 65:35 to 0:100. When a is La and the atomic ratio of O:N is in the interval from 65:3.5 to 0:100. Anions that can serve as 7 atoms are O2" and N3". The anion C4" also can be mixed with N3" or with a mixture of O2" and N3" and serve as y atoms. The glass according to the invention has a hardness value above 5 Gpa, preferably above 9,9 Gpa and more preferably above 12,3 Gpa. All of the obtained glasses showed hardness values above 5,0 Gpa, and the highest obtained hardness value was 13,0 Gpa. As an example, one material, with the composition La4.gSi3.2O5.6Ng.o, showed a hardness value above 10,6 Gpa. The hardness can be further improved by thermal treatment, in order to relieve internal stresses of the quenched glass, and by optimisating of the chemical compositions. The glass according to the invention has a refractivity index above 1,4, preferably i above 1,9 and more preferably above 2,2. The highest refractivity index yet disclosed for a silicate glass, was observed for the glass material of the invention. The obtained glasses according to the invention has a refractivity index above 1,4 and at least one of the glasses, with the composition La^gSis^O^gNg.o, showed a refractivity index of 2,20. By optimisating the chemical composition, especially with respect to the glass > modifiers further improvement of the refractivity index can be expected,. Glasses with magnetic or magneto-optic properties can be obtained wherein the jjjlass modifier, a, is a magnetic element such as Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, ,Yb, Lu, Pa, TJ and MIL By using these elements in the synthesis, elements with known strong paramagnetic field are introduced in the glass according to the invention. The synthesis and analysis of one of those oxonitride glasses containiijig a magnetic element is described in example 3 for the sample with the composition! Elements such as silicon, aluminium and boron, together with oxygen and nitrogen, form the network structure of the glass. Other elements usually with higher ionic radii and higher coordination numbers are named glass modifiers. The elements usually used as glass modifiers in oxosilicate glass are sodium, lithium, potassium, calcijim, strontium, barium, lanthanides, lead, bismuth and tin. The elements that are most suitable as glass modifiers in nitride based glass are alkali metals, alkaline earth metals, rare earth metals and in some cases transition metals. Another reason that makes some glass modifiers more suitable than others is their vapour pressure at higher temperatures. If alkali metals such as Na, K and Rb are used as glass modifiers it is preferable to use the glass modifier in excess, since evaporation of the alkali metal can occur, and/or applying higher nitrogen pressure in order to prevent possible evaporation of the alkali metal. The vapour pressure of the alkali metal decreases with decreasing atomic number. A further aspect of the present invention is a nitride glass which possesses magnetic and/or magneto-optic properties according to the second aspect of the present invention, wnerein tne glass mocuner, a, is at least one magnetic element such as Uc, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Pa and U. j The syntheses of nitrogen rich silicate glass were performed using mixtures of a \ metals, Si3N4, Si02, A1N and BN. The metals used in the synthesis procedure are ; electropositive and react with the N2 gas used to form nitrides. Elements such as Bai is probably transformed to different nitrides and sub-nitrides and most of the rare earth metals transform to LnN stoichiometric compounds. The p atoms are inserted in the mix in step a) as a chemical compound in the form of nitrides and oxides such as Si3N4, Si02, AIM and BN. The Si-base could be Si3N Any electropositive element can be used as glass modifier, a is preferably chosen i from the group of Be, Na, K, Rb, Zr, Hf, Nb, Ta, W, Mo, Cr, Fe, Co, Ni, Zn, Pb, Bi Lu, Mg, Y, Sc, Nd, Gd, Eu, Er, Tb, Tm, Dy, Yb, Th, Pa, U, Ca, Sr, Ba, La, Pr, Ce, Sm, Mn and Ho. Further, a is more preferably chosen from the group of Lu, Mg, Y, S0, Nd, Gd, Eu, Er, Tb, Tm, Dy, Yb, Th, Pa, U, Ca, Sr, Ba, La, Pr, Ce, Sm, Mn and Ho. Yet further, a is most preferably chosen from the group of Ca, Sr, Ba, La, Pr, Ce, Bm, Mn and Ho. ; The above mentioned elements could be used in the synthesis as an electropositive metal, or a nitride comprising an electropositive metal, or a compound comprising; an electropositive element that would transform into metallic state or a nitride when heated in nitrogen atmosphere. This means that La can be incoiporated in LaN. i Examples of such precursor materials are La metal, Ba metal, NdN, CaH2, etc, : The a atoms are usually introduced in their metallic form which are converted to I nitrides in N2 atmosphere, y are the anions in the glass network and are nitrogen ojr nitrogen together with oxygen with a composition that is dependent of the original chemical compositions used. By heating a composition comprising the electropositive metals, the main group element nitrides, and/or oxides, in nitrogen atmosphere and at high temperatures, ia melt with a specific chemical composition can be obtained, i.e. the electropositive metal is oxidised by the N2 molecule and reacted with the main group element nitrides and/or oxides and a nitride or oxonitride melt is eventually formed. This melt then contains cations of the glass modifiers e.g. Ba2+, La3+, Sin3, Gd3, Dy3+ and a network structure composed of Si(0,N)4 tetrahedra, A1(0,N)4 tetrahedra and B(0,N)3 trigonal building blocks in different ratio depending on the original composition of the mixture used. It is reasonable to assume that the anions (O,N) are apex atoms X11^ (bound with one Si atom) or bridging XJ2J (bound with two Si atoms) atoms and in some cases j they are isolated ions with chemical bonds only to the glass modifier ions as Xm (no bound Si atom). The synthesis mechanism could be analysed by trying different synthesis parameters such as time and temperature. The first part of the synthesis process is the nitridatjion of the electropositive metal, a, which could be used as glass modifier according tj> the formula below, herein a is La: 2La(s) -f N2(g) => 2LaN(s) This reaction occurs at temperatures far below 1000°C, and is in principle the only reaction that takes part at these low temperatures. At higher temperatures, typically i above 1500°C, the LaN starts to react with Si3N4 and Si02 and depending on the synthesis mixture, a melt is formed at a certain temperature. As soon as a partial m$lt is formed, the kinetic of the reaction increases significantly and the melt continues to dissolve rather inert nitrides such as SijN^ AlN and BN. At this stage, the synthesis mixture has formed a complete melt and the composition of the melt defines the \viscosity and the structure of the melt which is important for the glass transition temperature and the cooling rate needed in order to obtain an amorphous solid. The melt can now be quenched to a temperature below the glass transition temperature. The quenching can be performed in many different ways. One way is jto transferring the melted sample to a colder chamber, while a much more efficient cooling rate can be obtained by pouring the melted sample on a cold metal surface,! e.g. water cooled copper plate. In order to release the internal stresses, that can be presbnt in a quenched sample, the glass can be thermally treated at a temperature below the glass transition temperature. Such thermal treatment could give better mechanical properties. The obtained glass materials show very good thermal stability and are stable up temperatures as high as 1000-1500°C depending on the composition of the glass, the crystallisation process of the glass materials starts typically at ca. 1200"C. j In the present invention, the chemicals have been stored and mixed together in an argon filled glove box, in order to avoid oxidation of air and moisture sensitive chemicals such as Lrwnetals. The chemicals for every synthesis is weighted, mixed and grinded in the glove box and then transferred to a self made niobium crucible £nd then sealed with an air-tight plastic para-film. Many other crucibles that are inert to the melt formed and the precursor materials used can also be used. The filled niobium; crucible is transformed to the graphite furnace used for these syntheses. The graphjite furnace has two chambers. The upper chamber is the hot part of the furnace where tihe synthesis is made and the lower part of the furnace is the cooler part where to the \ sample is lowered to in order to quench the system to lower temperatures for fast j solidification of the oxonitride melt. The furnace is typically flushed three times vjith nitrogen gas before the heating program is started. The syntheses are always performed in -nitrogen gas atmosphere. The sample is heated up to the desired temperature, it could take from 1 second to 60 hours, typically within 2-4 hours, i i melt and the glass samples can be used for different analyses. Other furnaces that ban provide temperatures between room temperature and about 2000°C together with the use of nitrogen gas can also be used for the above mentioned synthesis purpose. Tjhe possibility of quenching the sample below the glass transition temperature is also ^n important feature for a furnace which could be used for the synthesis of the invenjed glass. The chemicals that can be used for the synthesis of nitride glass are for example • SiOi A1N, A1203, BN, B203 and metals such as rare earth metals, alkaline metals and alkaline earth metals. The precursor materials can be changed in a various ways. The most important thing is to obtain the nitrides that are needed in the reaction at a higher temperature when the melt is formed. The goal is to get the right oxygen/nitrogenj composition in the final melt that is quenched to form the glass phase. An especially preferred glass is when a comprises La and (3 comprises Si. In a third aspect, the glass material of the invention can be used in a variety of applications. A first embodiment of the third aspect of die present invention is as a surface coating for providing improvement of mechanical properties on an object such as eye-glassjes, watches and as glaze, with desired colours, on different ceramics. I A second embodiment of the third aspect of the present invention is as synthetic I gemstones. The combination of high refractivity index and the possibility of colouring the glass material by using different f-elements, together with good mechanical ; properties makes this novel glass type a good material for usage as synthetic \| gemstones. \| A third embodiment of the third aspect of the present invention is as magneto-optical device wherein A is at least one magnetic element such as Ce, Pr, Nd, Sm, Eu, Gdj Tb, Dy, Ho, Er, Tm, Yb, Lu, Pa, U and Mn. High concentrations of strongly magnetic elements makes this novel glass type very suitable as magneto-optical component^ for usage in CD and/or DVD technology. The Verdet coefficient is the parameter which defines the Faraday rotation or magneto-optic effect, which is the rotation of the pllaae of polarised light passing through a material when that material is exposed to an external magnetic field. The Verdet coefficient of a glass varies linearly with { concentration for mixtures of different rare earth ions and since much higher \| concentrations of rare earth ions can be incorporated in this novel glass type compared to traditional oxosilicate glasses, the Verdet constant is expected to be much largeir for the title glass with magnetic rare earth ions. A fourth embodiment of the third aspect of the present invention is as fiber optics! as well as other optical data transfer components. This can be achieved due to the high refractivity index in the novel glass, as high as 2,20. j I A fifth embodiment of tke third aspect of the present invention is as optical devices such as optical lenses. One of the most important physical properties desired for production of optical lenses is high refractivity index. The novel glass compound) has the highest refractivity index ever observed for silicate glass (n = 2,20). Typical yalues for refractivity index in ordinary oxosilicate glass is n K 1,4. The extremely high refractivity index of the invented glass is probably due to high concentrations of Highly polarisable ions such as La3+ and/or Ba2+, which easily can be obtained by this ne~jv synthesis procedure. j I A sixth embodiment of the third aspect of the present invention is as sintering \| additives for ceramic sintering. The properties of the glass found in the grain j I boundaries of sialons is crucial for the mechanical properties of the ceramics, Sinfe this novel glass possesses good mechanical properties such as high hardness as w£ll as high thermal stability it would be favourable in usage as sintering additives for salons as well as other nitrides and oxonitrides.j A seventh embodiment of the third aspect of the present invention is its usage as ; bioceramics, such as an implant This novel glass can be used in composite materials, i together with other compounds, for usage as bioceramics in different implants. It \s favourable due to low chemical reactivity in combination with good mechanical properties. ! Examples In the following the invention will be described in more detail by means of examples which are provided for illustrative purposes ouly and are not intended to limit the scope of the invention. The samples were examined using scanning electron microscopy in combination jvith j EDX analysis, X-ray powder diffraction for confirmation of the amorphous state 6f the samples, hardness measurements by indentation experiments, determination of thfc refractivity index by measuring the Brewster angle, chemical analysis of the oxygen and nitrogen content, oxidation behaviour, and magnetic susceptibility. The samples to be analysed in the electron microscope were mounted in bakelite,\| polished and carbon coated in order to avoid local charges. The microstructures ahd the metal compositions were analysed in a JEOL JSM 820 equipped with a LINK AN10000 EDX analyser system. j A focusing Huber Guilder 670 X-ray camera with a CuKct radiation source was usecjl. for detecting the existence or proving the absence of crystalline phases in the glass j samples. The XRPD patterns were collected in the 29 range 4-100° witih a step size The hardness of the new glass materials were analysed using Vickers hardness i measurements. A pyramidal diamond indenter with an applied load of 1000 grams vyas used. Three to five indentations were performed on each specimen. The samples wejre examined afterwards by light microscope and the diagonal lengths of the indentatiojiis were measured. The mean diagonal average length of each indentation was used for the calculation of the Vickers hardness using the following formula: Hv = (1854kgf. um2/gf.mm2)F/d2 : where F is the test load in grams and d is the mean diagonal length of the indentatioh, expressed in microns. A test load of 1000 grams and a mean diagonal length of the indentation of 40 urn would give a hardness value of Hv = 1159kgf/mm2. The Vickers hardness can be converted into SI units by the following formula: H = Hv kgf7mm2 [(9.807 N/kgf)/(10-6m2/mm2)] where H is the hardness in Pa. The oxygen/nitrogen content was analysed using a Leco Detector (TV-436DR) chemical analysis equipment. The glass samples were analysed using a combustion technique. By heating the sample in a graphite crucible oxygen and nitrogen atoms \| leave the sample as gaseous species. The oxygen atoms react with the graphite cruqible and forms carbon dioxide and is analysed by measuring the infrared absorption. The nitrogen atoms leave as N2 molecules and is analysed by measuring the thermal conductivity. One of the most important properties of amorphous materials is the propagation cj>f light through the solid and the change of direction of light between two different ! media. These properties can be defined by the refractivity index of the material g}ven at a certain wavelength. The refractivity index can be measured by different j techniques. The technique used for these glasses is the measurement of the Brewpter angle. The angle between the incident and reflected light where the maximum polarisation occurs is called the Brewster angle or polarising angle 0%. The ! relationship between the Brewster angle and the refractivity index is given by thd equation: = n where n is the refractivity index. Example, 1, synthesis of oxonitride glass with the composition La^Sij^O^jSf^n sjndjts optical and mechanical properties: A mixture of La metal, Si02 and Si3N4 was weighted and carefully grinded in an argon filled glove box. The composition of the mixture used was 615,4 mg La, 177,4 rag • SiOj and 207,2 mg Si3N4- The grinded mixture was transferred to a niobium tube! with one end sealed. The niobium tube was then covered by para-film in order to avoiji oxidation of La metal by air when transported to the graphite furnace. The fumacje was flushed with nitrogen gas three times before the heating program was started. Th^ sample was heated up to 1750DC from room temperature during 2 hours, kept at tjhis temperature for 22 hours and finally quenched by lowering the sample to the cold part of the furnace. After the furnace temperature was lowered to room temperature trie sample was removed from the furnace chamber. 5 mm large pieces of the obtained glass sample were used for EDX analysis and measurements of the refractivity index as well as hardness measurements. The mct^l composition obtained from the EDX analysis of a polished and carbon coated surface were found to be 48(±1 sdv) at% La and 52(±1 sdv) at% Si. This result indicates a \| minor loss of silicon during the synthesis due to the relative high temperature and l i revealed a homogenous glass sample, free of any crystalline phases. The refractivity index was found to be n - 2,20(7) calculated from the measured i Brewster angle 65,6°. This extremely high value of the refractivity index is the highest value ever found for a silicate based glass. The indentation experiments used for the hardness testing resulted in a hardness value of 10,6 Gpa for the above mentioned sample. Example 2, synthesis of oxonitridalummosilicate glass with the composition .Oo N The glass sample with the composition La^gSia^AI^O^N^o was synthesised by j mixing 787,6 mg La metal, 360,5 mg SiO2,122,9 mg A1N and 46,8 mg Si3N4 \| thoroughly in an argon filled glove box. The reaction mixture was then transferred jinto a niobium tube with one sealed end, which was covered with para-film in order to i i avoid oxidation of La metal by air while transporting it to the graphite furnace for freat i treatment. j The graphite furnace was flushed with nitrogen gas three times before starting the heat treatment. The sample was heated up to 1750°C from room temperature during 2 hours, held at this temperature for 30 hours and quenched by lowering the sample to the cool chamber of the graphite furnace. The obtained glass sample was removed from the graphite furnace when it had reached room temperature, and cut into ~5 mm laree pieces for further polishing and used for different analyses purposes. Scanning electron micrographs as well as X-ray powder diffraction patterns unambiguously showed a homogenous glass sample with no traces of crystalline phases. The EDX analysis of a carbon coated polished surface gave the following i metal composition: 46(±1 sdv) at% La, 33 (±1 sdv) at% Si and 22(±1 sdv) at% At The 0:N composition was found to be 65:35, which together with the metal composition gives a chemical stoichiometry of La^Sis^jAl^C^N^o- The refractivity index calculated from the measured Brewster angle was found to be 1,95(2), which corresponds to a Brewster angle of 62,8°. The hardness value obtained from the indentation experiments was 10,3 Gpa. Example 3. synthesis of the oxonitride glass with the composition and its optical, mechanical and magnetic properties: T- A batch of 1,0 gram mixture containing Sm, SisN (SiN^) and SiOj with the mo^ar ratio of Sm:SiNv3:Si02 corresponding to 7,33:5:5. The mixture was thoroughly \| grinded in an argon filled glove box transferred to a niobium tube with one sealed end and heat treated in a graphite furnace in nitrogen atmosphere. The mixture was hi jated up to 1 75 0°C during two hours, held at this temperature for 22 hours and then \| quenched to a temperature below the glass transition temperature by lowering th4 sample to the colder chamber of the graphite furnace. The sample was removed fjrom the furnace when it was cooled down to room temperature and 5 mm large piece^ wer i cut out for different analyses. Scanning electron micrographs as well as X-ray powder diffraction patterns unambiguously showed a homogenous glass sample with no traces of crystalline I ! phases. The EDX analysis of a carbon coated polished surface gave the following metal composition: 58(±1 sdv) at% Sm and 42(±1 sdv) at% Si. The O:N composition was assumed to be the same as found for the corresponding lanthanum containing glass, which would give an O:N ratio of 45:55. The O:N composition together wiith the metal composition gives a chemical stoichiometry of Sm^gSi^O^oNv^. The refractivity index calculated from the measured Brewster angle was found to be 2,03(2), which corresponds to a Brewster angle of 63,8°. The hardness value obtained from the indentation experiments was 11,4 Gpa. The magnetic susceptibility measurements gave a paramagnetic signal and temperature dependence typical for Sm3+ containing samples. Sm3+ is a magnetic ion, thereby showing that high concentrations of the magnetic ions can be obtained. The susceptibility curve agreed well with the temperature dependent susceptibility found for Sm203. Example 4, synthesis of tfac oxonitridoborosilicate with the nominal composition A mixture of 1,5752 g La metal, 0,721 g Si02> 0,0468 g Si3N4 and 0,075 g BN was\| thoroughly grinded in an argon filled glove box. The grinded mixture was transfenjed to a self made niobium crucible. The crucible was covered with para-film and transported to a graphite furnace for thermal treatment The graphite furnace was flushed with nitrogen gas three times before starting the heat treatment program, T sample was then heated to 1600°C during 2 hours, held at this temperature for 30 hours, tiie temperature was then raised to 1750°C and held at this ramp for 1 hour before quenching to a temperature below the glass transition temperature by lowering the sample to the colder furnace chamber. The sample was removed from tibe fuma\|ce i when the room temperature was reached and 5 mm large pieces were cut out for different analyses. Scanning electron micrographs as well as X-ray powder diffraction patterns unambiguously showed a homogenous glass sample with no traces of crystalline phases. The above mentioned analysis show clearly that the BN powder also was dissolved in the glass sample and is therefore integrated in the amorphous glass structure. The results clearly shows that the physical and mechanical properties of oxide glasses such as hardness, elastic modulus, fracture toughness, and glass transition temperature are improved/increased, when the atomic structure of the network is strengthened lj>y replacing oxygen atoms by nitrogen atoms. Further, the results shows mat a very high refractivity index could be achieved. Further examples i j Chemical composition of investigated glasses is shown below. All compositions were melted at 1750°C for 22 hours. G indicates that glass is formed and C indicates that also a crystalline phase is present. Chemical composition of investigated glasses is shown below. All compositions wjere melted at 1500°C for 18 hours, and then increased the temperature at 1750°C for 30 min. and hold at this temperature for 30 min. and quenched to room temperature in a cold chamber of furnace, under the flow of nitrogen gas. Chemical composition of investigated glasses is shown below. All compositions wjere melted at 1700 °C and 1200°C for 19.5 hours (the compositions were melted at 17(pO i °C for (2+12) hours and than at 1200 °C for 4 hours and than last run was done at 1700 °C for 1.5 hours). Basis of one gram. Partially glass is indicated when a glass phases is formed and some of the resulted material is crystalline. The crystals are incorporated in the glass mass. There is about 30-80 volume percent glass in the below mentioned synthesis examples. Samples were melted at 1750°C for 30 hours, and then subsequently cool to roo temperature (inside of the furnace under the flow of N2). KB. All above composition were melted in graphite holder (small in size) and samples were inside of the Nb. Tube as well as during cooling N2 were insert through lower\cold chamber instead of hot chamber. Sample SmE3, SmP9, GdE3 and GdP9 were melted at 1750°C for 22 hours and .... and GdA2 were melted at 1750°C for 30 hours, subsequently cool to room temperatlire (inside of the furnace under the flow of Nj) See note. NB. All above composition were melted in graphite holder (small in size) and samples were inside of the Nb tube, as well as during cooling N2 were insert through lower\cold chamber instead of hot chamber. Samples were melted at 1750°C for 22 hours, subsequently cool to room temperahuje (inside of the furnace under the flow of N2) See note. NB. All above composition were melted in graphite holder (small in size) and sarnp! les i were inside of the Nb tube3 as well as during cooling Nj were insert through ! lower\cold chamber instead of hot chamber. We Claim: 1. A nitride glass having high refractivity index and good hardness values with the general formula αxßyγz wherein a is at least one electropositive element chosen from the group of alkali metals Na, K and Rb, alkaline earth metals Be, Mg, Ca, Sr and Ba, transition metals Zr, Hf Nb, Ta, W, Mo, Cr, Fe, Co, Ni, Zn, Sc, Y, Mn and La, main group elements Pb, Bi, and f elements Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Pa and U; ß comprises Si and optionally at least one of the elements of the group of B, Ge, Ga and Al; and Y is N or N together with 02 whereby the atomic ratio of O:N is in the interval from 65:35 to 0:100, wherein the ratio α:ß is in the interval from 30:70 to 60:40, preferably in the interval from 41:59 to 60:40, wherein the ratio ß:γ is in the interval from 33:67 to 22:78. 2. A nitride glass as claimed in claim 1, wherein a is chosen from the group of Lu, Mg, Y, Sc, Nd, Gd, Eu, Er, Tb, Tm, Dy, Yb, Th, Pa, Ca, Sr, Ba, La, Pr, Ce, Sm, Mn and Ho. 3. A nitride glass as claimed in claims 1 and 2, wherein a is chosen from the group of Ca, Sr, Ba, La, Pr, Ce, Sm, Mn and Ho. 4. A nitride glass as claimed in anyone of claims 1 to 3, wherein ß is Si. 5. A method for preparing a nitride glass as claimed in anyone of claims 1 to 4, comprising the steps of a) mixing chemicals of the kind such as herein described corresponding to the desired composition of the kind such as herein described by using a as a pure metal and/or the corresponding metal nitrides or metal hydrides or any other compound that transforms to the corresponding nitride in nitrogen atmosphere during the synthesis; b) heating said compounds to at least 1000°C in the presence of nitrogen gas, thereby obtaining a melt; c) maintaining the temperature of step b) until the mixed chemical compounds have formed a homogenous melt; and d) cooling the melt to a temperature below the glass transition temperature and using a cooling rate, that is sufficient in order to obtain a glass phase. 6. A method as claimed in claim 5, wherein the temperature in steps b) and c) is above 1500 °C, and preferably above 1800 °C. 7. A nitride glass with the general formula wherein: a is at least one electropositive element chosen from the group of alkali metals Na, K and Rb, alkaline earth metals Be, Mg, Ca, Sr and Ba, transition metals Zr, Hf Nb, Ta, W, Mo, Cr, Fe, Co, Ni, Zn, Sc, Y, and La, main group elements Pb, Bi, and f elements Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Pa and U; P is chosen from at least one of the elements of the group comprising Si, B, Ge, Ga and Al; and Y is N or N together with O, whereby the atomic ratio of O:N is in the interval from 65:35 to 0:100, wherein the nitride glass is prepared by a method comprising the steps of; a) mixing chemicals corresponding to the desired composition by using a as a pure metal and/or the corresponding metal nit-ides or metal hydrides or any other compound that transforms to the corresponding nitride in nitrogen atmosphere during the synthesis; b) heating said compounds to at least 1000 °C, preferably above 1500 °C, and more preferably above 1800 °C, in the presence of nitrogen gas, thereby obtaining a melt; c) maintaining the temperature of step b) until the mixed chemical compounds have formed a homogenous melt; and d) cooling the melt to a temperature below the glass transition temperature and using a cooling rate, that is sufficient in order to obtain a glass phase.

Full Text

Technical field
The invention relates to a nitride glass, a method for preparing a nitride glass and the
use of the glass.
Technical background
Silicon nitride and sialon based materials are recognised as ceramics in high temperature engineering applications due to their high chemical and thermal stability combined with superior mechanical properties. In these systems, self-diffusion processes are relatively slow and they may require an oxide-sintering additive to provide conditions for liquid phase sintering. During sintering, the additive reacts with silica on the surface of the silicon nitride particles and some of the nitride forms an oxynitride liquid, which is converted into a glass phase during cooling. The composition and volume fraction of such oxynitride glass phases strongly influence the properties of the materials.
The glass forming regions have been investigated by many different researchers. The existence of sialon glass was first reported by K. H. Jack, J. Mat. Sci. Rev. 11 (1976) 1135-1158. T. H. Elmer, and M. E. Nordberg, J.Amer. Cer. Soc. 50 (1967) 275-279, introduced nitrogen into a high silica glass by heating the melt in NH3 atmosphere. H, 0. Mulfinger, J. Amer. Cer. Soc. 49 (1966) 462-467 produced nitrogen containing soda-lime glass by adding 81^4 to the synthesis mixture. The effect of nitrogen concentration in silica glass on the hardness properties was studied by Shillito et al, Cer. Soc. 63 (1978) 537. It was suggested mat the incorporation of N2 into a silica glass affects the material properties due to the difference in the bonding strength of Si-N compared to Si-0.
By comparing Y-sialon glasses with SiO2-Y203~Al203 glasses an increase in hardness could be pointed out by introducing nitrogen in the silica glass, where oxygen atoms
are partly replaced by N". me naroness 01 tne glasses was increased wiin an increase of nitrogen content,
R. E. Loehman, J. Non-Crys. Solids 56 (1983) 123-134 disclosed that mixtures of oxides and nitrides could be melted and quenched to form glass. By introducing nitrogen into the oxosilicate glass, several material properties were improved, such as increase in the glass transition temperature, hardness, fracture toughness, elastic modulus and chemical durability.
The dissolution of nitrogen in oxosilicate melts was further studied by E, A. Dancy andD. Janssen, Canadiaa Metallurgical Quarter 15[2] (1976) 103-110, who reacted CaO-Al203-SiO2 at 1550°C in 1 atm. N2 gas. The amount of 0,25 to 2,5 wt% nitrogen could be incorporated by this technique while as high as 4 wt% nitrogen was incorporated by dissolving solid Si3N4 in the melt. The nitrogen concentration in the melt is probably due to the strong and much favourable triple bond in the N2 molecule.
Jack et al. disclosed bulk samples of oxynitride glass obtained by pressure-less heat treatment of a mixture of 14Y2O3-59Si02-27AlN hi a boron nitride crucible at 1700PC in nitrogen atmosphere. This sample was found to have a refractive index of 1,76 and a nitrogen concentration of 9 at% corresponding to an O:N ratio of 86:14.
Silicate glass is usually made from oxosilicates. The highest possible condensation degree in pure oxosilicates is found for Si02,wherein every oxygen atom is coordinated by two silicon atoms. It is possible to form glass from pure Si02-
This form of glass has been found to have many superior physical properties, such as a high melting point, good mechanical properties and transparency for UV photons. However, a high synthesis temperature is needed for the fonnation of SiO2 glass. Glass modifiers such as Ha*, K+ and Ba2+ are added to SiO2 in different concentrations in order to lower the melting temperatures and the manufacturing cost. By introducing! glass modifiers, the network structure of SiO2 is partially broken and some of the
oxygen atoms are therefore connected only to one silicon atom. Oxygen atoms connected to only one silicon atom are called apex atoms and oxygen atoms connected to two silicon atoms are named bridging atoms. The three dimensional Si-0 network in the glass can be maintained when only one out of four oxygen atoms of the Si04 tetrahedra are apex. At least three oxygen atoms must be bridging between two silicon atoms to get a three dimensional network.
This restriction of the condensation degree makes it possible to form oxosilicate glass only in the composition range Si02 -MxSiO2,5. The highest concentration of the The concept of introducing nitrogen into the glass chemistry has previously been lused in sialon glasses. By quenching melts of M-Si-Al-O-N from high temperatures, glass phases of sialons with glass modifiers such, as La3* and Y34" were obtained. The composition limit concerning Ln (lanthanide) content, which were used as the glaiss modifiers, and nitrogen content was reached with the composition LasSijoAljOj-^Ns, described by N. K. Schneider, H. Lemercier and S. Hampshire, Materials Science! Forum, 325-326 (2000) 265-270. This composition gives the highest lanthanum and nitrogen content ever obtained in a nitride based glass at ambient pressure. The cationic composition given in atomic percent is then La; 25%, Si: 50% and Al: 25% and the anionic composition given in the same way is O : 84,2% and N: 15,8%. The synthesis technique used for preparation of such glasses has limited the nitrogen content as well as the glass modifier content (lanthanum in the example mentioned above).
Accordingly, the glass materials that are present today have a nitrogen content corresponding to the 0:N ratio of 84,2:15,8. However, since demands for new glass materials having higher strength and improved physical properties in other respects, not least for various optical, ceramical and coathag-technological applications,
continuously are raised, it would be a great advantage to provide new materials witji even better properties.
!
One oxonitride glass with higher lanthanum and nitrogen content has been disclosed by A. Makishima, M. Mitomo, H. Tanaka, N. li and M. Tsutsumi, Yogyo-Kyokai-Shi 88[11] (1980) 701, possible to synthesis only at high nitrogen pressure (30 atm.)- the composition of this glass have been reported as La^Sizo.oC^xsNu^ corresponding to a La;Si ratio of 49:51 and an O:N ratio of 70:30.
W. Schnick et al. Chem., 9 (1999) 289 introduced a route for introducing nitrogen Into the silicate chemistry other than the obvious reaction of the silicate melt with NI gas for synthesis of crystalline nitridosilicates, oxonitridosilicates and oxonitridoalumiiiosilicates, i.e. not glass material^ by using electropositive metals; together with silicon diimide (SiCNH)2) in a radio frequency furnace. The above i mentioned synthesis route was accordingly used only for producing crystalline phajses.
The glass materials described above have certain limitations in chemical composition regarding both nitrogen content as well as concentration of glass modifiers. The chemical composition of such material is a crucial parameter defining the physical properties and for that reason also different possibilities in applications.
A problem with nitrogen containing glass today is that there are requirements for qven better physical properties of glass than is known today. There are no known methods for increasing the nitrogen content' of the glass and thereby try to improve its i properties. The method of Makishiina et al has yielded the highest known nitrogen-content, but that method has the disadvantage of requiring complicated equipment and is expensiv Summary of tfae invention
It is the purpose of the present invention to provide a new glass material, and a method for its manufacturing, thereby solving the problems posed above and meeting the demands on this point
The present invention is directed to overcoming the problems set forth above. This is achieved by producing nitride glass using electropositive elements in their metallic state, as nitrides or any other compound that would transform into metallic state or a nitride when heated in nitrogen atmosphere preferably together with silicon nitride and silicon oxide.
In a first aspect, the present invention relates to a nitride glass. The new glass material shows clearly surprising and excellent properties such as extremely high refractiviity index and very good hardness values.
In a second aspect, the present invention relates to a method for preparing a nitride glass, without using high nitrogen pressure during the synthesis. A manufacturing method for nitride glasses is provided, wherein the nitrogen content is possible toi be increased, compared to known glass material manufacturing methods. The atomic ratio of O:N is in the interval from 65:35 to 0;100.
In a third aspect the present invention relates to the use of a nitride glass in several different applications, e.g. in a surface coating for providing an improvement of mechanical properties on an object such as eye-glasses; in watches and as glaze on
different ceramics; in synthetic gemstones; in fibre optics and other optical data i transfer components; in an optical device, such as an optical lens; in a sintering !
additive for ceramic sintering; in bio-ceramics, such as an implant; in a magneto-optical device, wherein the glass modifier is at least one magnetic element such a|s Dy, Nd, Sm, Tb or Pr as well as a component in a CD and/or a DVD device.
Thus, due to the high nitrogen content of the glasses of the invention, unique features of improved mechanical properties are provided, such as a high hardness value, a high melting point, and improved physical properties such as a high refractivity index. Further, strong paramagnetic glasses can be obtained by using magnetic f-elements as glass modifiers, whereby high concentrations of the magnetic ions can be obtained;
Detailed description of the invention
In the first aspect, the present invention relates to a nitride glass with the general
formula o^py^, wherein
a is a at least one electropositive element chosen from the group of alkali metals Na, K
and Kb, alkaline earth metals Be, Mg, Ca, Sr and Ba, transition metals Zi, Hf, Nb, Ta,
W, Mo, Cr, Fe, Co, Ni, Zn, Sc, Y, and La, main group elements Pb, Bi, and f elements
Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Pa and U;
P is chosen from the group of Si, B, Ge, Ga and Al; and
Y is N or N together with O, whereby the nitrogen content given as atomic ratio of O:N
is higher than 65:3 5.
The atomic ratio of O:N is preferably higher than 65:35, more preferably higher than 41:59 and most preferably higher than 20:80.
A preferred embodiment is when a is La and (5 comprises Si and the atomic ratio of 0:N is in the interval from 65:35 to 0:100.
In a second aspect, the present invention relates to a method for preparing such a nitride glass comprising the steps of
a) mixing chemicals corresponding to the desired composition by using a as a pure metal and/or the corresponding metal nitrides or metal hydrides or any other compound that transforms to the corresponding nitride in nitrogen atmosphere during the synthesis;
b) heating said compounds to at least 1000 °C in the presence of nitrogen gas, thereby
obtaining a melt;
c) maintaining the temperature of step b) until the mixed chemical compounds have
formed a homogenous melt; and
d) cooling the melt to a temperature below the glass transition temperature and usitig a
cooling rate, that is sufficient in order to obtain a glass phase.
The nitrogen gas is present as long as the sample has a temperature higher than 1000°C in order to avoid dissociation or oxidation of the glass sample. The heating in step' b, is obtained during 1 second to 60 hours.
The temperature in step c, is maintained until equilibrium is reached, preferably diiuring 4 to 24 hours. The time will depend on various parameters, such as the furnace used in the process and the sample composition.
The synthesis temperature, or melting temperature, of step b and c is preferably above 1500°C and more preferably above 1800°C, depending on the composition of the melt. Even higher temperatures could be used
Standard furnaces could be used in the method for preparing a nitride glass according to the present invention. However, it is important, that the furnace can operate at the temperatures from room temperature to 2000°C. In the examples presented below: a graphite furnace was used. Other furnaces which one could achieve equally high temperatures, with the possibility of quenching the samples, in nitrogen atmosphere can also be used.
The skilled person would know what type of crucible material to choose since the temperature of the melt can be above 1500°C. The material used in the crucible should be inert to the melt at temperatures at least above the synthesis temperature used j depending on the glass. Thus, the compounds used in the method should be place boron nitride. These materials are possible to use due to their high melting points as i
well as being rather inert to the melted samples formed in the synthesis route. So far
the inventor has tried niobium, tungsten, molybdenum and tantalum as well as boron
nitride. In the case of BN a small reaction could be observed between the melt and tije
crucible. This shows at the same time that BN can be introduced in the nitride based
glass. ;
New nitride glasses can by using this new synthesis approach be produced with a large variety of chemical compositions, a is the glass modifier, or the element that is not ] involved in the network structure, p is the cation that together with the anion y form \ the network structure. The ratio a:p is in the interval from 30:70 to 60:40, preferably 51:49 to 60:40, depending upon the composition. The ratio P:y is in the interval fronji 33:61 to 22:88. The atomic ratio of 0:N is in the interval from 84:16 to 0:100, preferably in the interval from 65:35 to 0:100. When a is La and the atomic ratio of O:N is in the interval from 65:3.5 to 0:100.
Anions that can serve as 7 atoms are O2" and N3". The anion C4" also can be mixed with N3" or with a mixture of O2" and N3" and serve as y atoms.
The glass according to the invention has a hardness value above 5 Gpa, preferably above 9,9 Gpa and more preferably above 12,3 Gpa.
All of the obtained glasses showed hardness values above 5,0 Gpa, and the highest obtained hardness value was 13,0 Gpa. As an example, one material, with the composition La4.gSi3.2O5.6Ng.o, showed a hardness value above 10,6 Gpa. The hardness can be further improved by thermal treatment, in order to relieve internal stresses of the quenched glass, and by optimisating of the chemical compositions.
The glass according to the invention has a refractivity index above 1,4, preferably
i
above 1,9 and more preferably above 2,2. The highest refractivity index yet disclosed for a silicate glass, was observed for the glass material of the invention. The obtained
glasses according to the invention has a refractivity index above 1,4 and at least one of the glasses, with the composition La^gSis^O^gNg.o, showed a refractivity index of 2,20. By optimisating the chemical composition, especially with respect to the glass > modifiers further improvement of the refractivity index can be expected,.
Glasses with magnetic or magneto-optic properties can be obtained wherein the jjjlass modifier, a, is a magnetic element such as Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, ,Yb, Lu, Pa, TJ and MIL By using these elements in the synthesis, elements with known strong paramagnetic field are introduced in the glass according to the invention. The synthesis and analysis of one of those oxonitride glasses containiijig a magnetic element is described in example 3 for the sample with the composition!
Elements such as silicon, aluminium and boron, together with oxygen and nitrogen, form the network structure of the glass. Other elements usually with higher ionic radii and higher coordination numbers are named glass modifiers. The elements usually used as glass modifiers in oxosilicate glass are sodium, lithium, potassium, calcijim, strontium, barium, lanthanides, lead, bismuth and tin. The elements that are most suitable as glass modifiers in nitride based glass are alkali metals, alkaline earth metals, rare earth metals and in some cases transition metals.
Another reason that makes some glass modifiers more suitable than others is their vapour pressure at higher temperatures. If alkali metals such as Na, K and Rb are used as glass modifiers it is preferable to use the glass modifier in excess, since evaporation of the alkali metal can occur, and/or applying higher nitrogen pressure in order to prevent possible evaporation of the alkali metal. The vapour pressure of the alkali metal decreases with decreasing atomic number.
A further aspect of the present invention is a nitride glass which possesses magnetic and/or magneto-optic properties according to the second aspect of the present
invention, wnerein tne glass mocuner, a, is at least one magnetic element such as Uc,
Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Pa and U. j
The syntheses of nitrogen rich silicate glass were performed using mixtures of a \ metals, Si3N4, Si02, A1N and BN. The metals used in the synthesis procedure are ; electropositive and react with the N2 gas used to form nitrides. Elements such as Bai is probably transformed to different nitrides and sub-nitrides and most of the rare earth metals transform to LnN stoichiometric compounds.
The p atoms are inserted in the mix in step a) as a chemical compound in the form of nitrides and oxides such as Si3N4, Si02, AIM and BN. The Si-base could be Si3N Any electropositive element can be used as glass modifier, a is preferably chosen i
from the group of Be, Na, K, Rb, Zr, Hf, Nb, Ta, W, Mo, Cr, Fe, Co, Ni, Zn, Pb, Bi
Lu, Mg, Y, Sc, Nd, Gd, Eu, Er, Tb, Tm, Dy, Yb, Th, Pa, U, Ca, Sr, Ba, La, Pr, Ce, Sm,
Mn and Ho. Further, a is more preferably chosen from the group of Lu, Mg, Y, S0,
Nd, Gd, Eu, Er, Tb, Tm, Dy, Yb, Th, Pa, U, Ca, Sr, Ba, La, Pr, Ce, Sm, Mn and Ho.
Yet further, a is most preferably chosen from the group of Ca, Sr, Ba, La, Pr, Ce, Bm,
Mn and Ho. ;
The above mentioned elements could be used in the synthesis as an electropositive metal, or a nitride comprising an electropositive metal, or a compound comprising; an electropositive element that would transform into metallic state or a nitride when
heated in nitrogen atmosphere. This means that La can be incoiporated in LaN. i Examples of such precursor materials are La metal, Ba metal, NdN, CaH2, etc, :
The a atoms are usually introduced in their metallic form which are converted to I nitrides in N2 atmosphere, y are the anions in the glass network and are nitrogen ojr nitrogen together with oxygen with a composition that is dependent of the original chemical compositions used.
By heating a composition comprising the electropositive metals, the main group element nitrides, and/or oxides, in nitrogen atmosphere and at high temperatures, ia melt with a specific chemical composition can be obtained, i.e. the electropositive metal is oxidised by the N2 molecule and reacted with the main group element nitrides and/or oxides and a nitride or oxonitride melt is eventually formed. This melt then contains cations of the glass modifiers e.g. Ba2+, La3+, Sin3*, Gd3*, Dy3+ and a network structure composed of Si(0,N)4 tetrahedra, A1(0,N)4 tetrahedra and B(0,N)3 trigonal building blocks in different ratio depending on the original composition of the mixture used. It is reasonable to assume that the anions (O,N) are apex atoms X11^ (bound with one Si atom) or bridging XJ2J (bound with two Si atoms) atoms and in some cases j they are isolated ions with chemical bonds only to the glass modifier ions as Xm (no bound Si atom).
The synthesis mechanism could be analysed by trying different synthesis parameters such as time and temperature. The first part of the synthesis process is the nitridatjion of the electropositive metal, a, which could be used as glass modifier according tj> the formula below, herein a is La:
2La(s) -f N2(g) => 2LaN(s)
This reaction occurs at temperatures far below 1000°C, and is in principle the only reaction that takes part at these low temperatures. At higher temperatures, typically
i
above 1500°C, the LaN starts to react with Si3N4 and Si02 and depending on the
synthesis mixture, a melt is formed at a certain temperature. As soon as a partial m$lt is formed, the kinetic of the reaction increases significantly and the melt continues to dissolve rather inert nitrides such as SijN^ AlN and BN. At this stage, the synthesis mixture has formed a complete melt and the composition of the melt defines the \viscosity and the structure of the melt which is important for the glass transition temperature and the cooling rate needed in order to obtain an amorphous solid.
The melt can now be quenched to a temperature below the glass transition
temperature. The quenching can be performed in many different ways. One way is jto transferring the melted sample to a colder chamber, while a much more efficient cooling rate can be obtained by pouring the melted sample on a cold metal surface,! e.g. water cooled copper plate. In order to release the internal stresses, that can be presbnt in a quenched sample, the glass can be thermally treated at a temperature below the glass transition temperature. Such thermal treatment could give better mechanical properties.
The obtained glass materials show very good thermal stability and are stable up
temperatures as high as 1000-1500°C depending on the composition of the glass, the
crystallisation process of the glass materials starts typically at ca. 1200"C. j
In the present invention, the chemicals have been stored and mixed together in an argon filled glove box, in order to avoid oxidation of air and moisture sensitive chemicals such as Lrwnetals. The chemicals for every synthesis is weighted, mixed and grinded in the glove box and then transferred to a self made niobium crucible £nd then sealed with an air-tight plastic para-film. Many other crucibles that are inert to the melt formed and the precursor materials used can also be used. The filled niobium; crucible is transformed to the graphite furnace used for these syntheses. The graphjite furnace has two chambers. The upper chamber is the hot part of the furnace where tihe synthesis is made and the lower part of the furnace is the cooler part where to the \ sample is lowered to in order to quench the system to lower temperatures for fast j solidification of the oxonitride melt. The furnace is typically flushed three times vjith
nitrogen gas before the heating program is started. The syntheses are always performed in -nitrogen gas atmosphere. The sample is heated up to the desired temperature, it could take from 1 second to 60 hours, typically within 2-4 hours, i i
melt and the glass samples can be used for different analyses. Other furnaces that ban
provide temperatures between room temperature and about 2000°C together with the
use of nitrogen gas can also be used for the above mentioned synthesis purpose. Tjhe
possibility of quenching the sample below the glass transition temperature is also ^n
important feature for a furnace which could be used for the synthesis of the invenjed
glass.
The chemicals that can be used for the synthesis of nitride glass are for example
•
SiOi A1N, A1203, BN, B203 and metals such as rare earth metals, alkaline metals and alkaline earth metals. The precursor materials can be changed in a various ways. The most important thing is to obtain the nitrides that are needed in the reaction at a higher temperature when the melt is formed. The goal is to get the right oxygen/nitrogenj composition in the final melt that is quenched to form the glass phase.
An especially preferred glass is when a comprises La and (3 comprises Si.
In a third aspect, the glass material of the invention can be used in a variety of applications.
A first embodiment of the third aspect of die present invention is as a surface coating
for providing improvement of mechanical properties on an object such as eye-glassjes,
watches and as glaze, with desired colours, on different ceramics. I
A second embodiment of the third aspect of the present invention is as synthetic I
gemstones. The combination of high refractivity index and the possibility of colouring
the glass material by using different f-elements, together with good mechanical ;
properties makes this novel glass type a good material for usage as synthetic |
gemstones. |
A third embodiment of the third aspect of the present invention is as magneto-optical
device wherein A is at least one magnetic element such as Ce, Pr, Nd, Sm, Eu, Gdj Tb,
Dy, Ho, Er, Tm, Yb, Lu, Pa, U and Mn. High concentrations of strongly magnetic
elements makes this novel glass type very suitable as magneto-optical component^ for
usage in CD and/or DVD technology. The Verdet coefficient is the parameter which
defines the Faraday rotation or magneto-optic effect, which is the rotation of the pllaae
of polarised light passing through a material when that material is exposed to an
external magnetic field. The Verdet coefficient of a glass varies linearly with {
concentration for mixtures of different rare earth ions and since much higher |
concentrations of rare earth ions can be incorporated in this novel glass type compared
to traditional oxosilicate glasses, the Verdet constant is expected to be much largeir for
the title glass with magnetic rare earth ions.
A fourth embodiment of the third aspect of the present invention is as fiber optics! as
well as other optical data transfer components. This can be achieved due to the high
refractivity index in the novel glass, as high as 2,20. j
I
A fifth embodiment of tke third aspect of the present invention is as optical devices such as optical lenses. One of the most important physical properties desired for production of optical lenses is high refractivity index. The novel glass compound) has the highest refractivity index ever observed for silicate glass (n = 2,20). Typical yalues
for refractivity index in ordinary oxosilicate glass is n K 1,4. The extremely high
refractivity index of the invented glass is probably due to high concentrations of Highly
polarisable ions such as La3+ and/or Ba2+, which easily can be obtained by this ne~jv
synthesis procedure. j
I
A sixth embodiment of the third aspect of the present invention is as sintering | additives for ceramic sintering. The properties of the glass found in the grain j
I
boundaries of sialons is crucial for the mechanical properties of the ceramics, Sinfe this novel glass possesses good mechanical properties such as high hardness as w£ll as
high thermal stability it would be favourable in usage as sintering additives for salons

as well as other nitrides and oxonitrides.j

A seventh embodiment of the third aspect of the present invention is its usage as ; bioceramics, such as an implant This novel glass can be used in composite materials,
i
together with other compounds, for usage as bioceramics in different implants. It \s

favourable due to low chemical reactivity in combination with good mechanical
properties.

!
Examples
In the following the invention will be described in more detail by means of examples
which are provided for illustrative purposes ouly and are not intended to limit the
scope of the invention.
The samples were examined using scanning electron microscopy in combination jvith
j
EDX analysis, X-ray powder diffraction for confirmation of the amorphous state 6f the
samples, hardness measurements by indentation experiments, determination of thfc
refractivity index by measuring the Brewster angle, chemical analysis of the oxygen
and nitrogen content, oxidation behaviour, and magnetic susceptibility. The samples to be analysed in the electron microscope were mounted in bakelite,| polished and carbon coated in order to avoid local charges. The microstructures ahd
the metal compositions were analysed in a JEOL JSM 820 equipped with a LINK AN10000 EDX analyser system. j
A focusing Huber Guilder 670 X-ray camera with a CuKct radiation source was usecjl. for detecting the existence or proving the absence of crystalline phases in the glass j samples. The XRPD patterns were collected in the 29 range 4-100° witih a step size The hardness of the new glass materials were analysed using Vickers hardness i measurements. A pyramidal diamond indenter with an applied load of 1000 grams vyas used. Three to five indentations were performed on each specimen. The samples wejre examined afterwards by light microscope and the diagonal lengths of the indentatiojiis were measured. The mean diagonal average length of each indentation was used for the calculation of the Vickers hardness using the following formula:
Hv = (1854kgf. um2/gf.mm2)F/d2 :
where F is the test load in grams and d is the mean diagonal length of the indentatioh, expressed in microns. A test load of 1000 grams and a mean diagonal length of the indentation of 40 urn would give a hardness value of Hv = 1159kgf/mm2. The Vickers hardness can be converted into SI units by the following formula:
H = Hv kgf7mm2 [(9.807 N/kgf)/(10-6m2/mm2)] where H is the hardness in Pa.
The oxygen/nitrogen content was analysed using a Leco Detector (TV-436DR) chemical analysis equipment. The glass samples were analysed using a combustion technique. By heating the sample in a graphite crucible oxygen and nitrogen atoms | leave the sample as gaseous species. The oxygen atoms react with the graphite cruqible and forms carbon dioxide and is analysed by measuring the infrared absorption. The

nitrogen atoms leave as N2 molecules and is analysed by measuring the thermal conductivity.
One of the most important properties of amorphous materials is the propagation cj>f light through the solid and the change of direction of light between two different ! media. These properties can be defined by the refractivity index of the material g}ven at a certain wavelength. The refractivity index can be measured by different j techniques. The technique used for these glasses is the measurement of the Brewpter angle. The angle between the incident and reflected light where the maximum polarisation occurs is called the Brewster angle or polarising angle 0%. The
!
relationship between the Brewster angle and the refractivity index is given by thd
equation:
= n
where n is the refractivity index.
Example, 1, synthesis of oxonitride glass with the composition La^Sij^O^jSf^n sjndjts
optical and mechanical properties:
A mixture of La metal, Si02 and Si3N4 was weighted and carefully grinded in an argon filled glove box. The composition of the mixture used was 615,4 mg La, 177,4 rag • SiOj and 207,2 mg Si3N4- The grinded mixture was transferred to a niobium tube! with one end sealed. The niobium tube was then covered by para-film in order to avoiji oxidation of La metal by air when transported to the graphite furnace. The fumacje was flushed with nitrogen gas three times before the heating program was started. Th^ sample was heated up to 1750DC from room temperature during 2 hours, kept at tjhis temperature for 22 hours and finally quenched by lowering the sample to the cold part of the furnace. After the furnace temperature was lowered to room temperature trie sample was removed from the furnace chamber.

5 mm large pieces of the obtained glass sample were used for EDX analysis and measurements of the refractivity index as well as hardness measurements. The mct^l composition obtained from the EDX analysis of a polished and carbon coated surface were found to be 48(±1 sdv) at% La and 52(±1 sdv) at% Si. This result indicates a | minor loss of silicon during the synthesis due to the relative high temperature and l i
revealed a homogenous glass sample, free of any crystalline phases.
The refractivity index was found to be n - 2,20(7) calculated from the measured
i Brewster angle 65,6°. This extremely high value of the refractivity index is the highest
value ever found for a silicate based glass. The indentation experiments used for the hardness testing resulted in a hardness value of 10,6 Gpa for the above mentioned sample.
Example 2, synthesis of oxonitridalummosilicate glass with the composition .Oo *N The glass sample with the composition La^gSia^AI^O^N^o was synthesised by j mixing 787,6 mg La metal, 360,5 mg SiO2,122,9 mg A1N and 46,8 mg Si3N4 | thoroughly in an argon filled glove box. The reaction mixture was then transferred jinto a niobium tube with one sealed end, which was covered with para-film in order to i
i
avoid oxidation of La metal by air while transporting it to the graphite furnace for freat
i
treatment. j
The graphite furnace was flushed with nitrogen gas three times before starting the heat treatment. The sample was heated up to 1750°C from room temperature during 2 hours, held at this temperature for 30 hours and quenched by lowering the sample to the cool chamber of the graphite furnace. The obtained glass sample was removed from the graphite furnace when it had reached room temperature, and cut into ~5 mm laree pieces for further polishing and used for different analyses purposes.

Scanning electron micrographs as well as X-ray powder diffraction patterns unambiguously showed a homogenous glass sample with no traces of crystalline
phases. The EDX analysis of a carbon coated polished surface gave the following
i metal composition: 46(±1 sdv) at% La, 33 (±1 sdv) at% Si and 22(±1 sdv) at% At The
0:N composition was found to be 65:35, which together with the metal composition gives a chemical stoichiometry of La^Sis^jAl^C^N^o- The refractivity index calculated from the measured Brewster angle was found to be 1,95(2), which corresponds to a Brewster angle of 62,8°. The hardness value obtained from the indentation experiments was 10,3 Gpa.
Example 3. synthesis of the oxonitride glass with the composition and its optical, mechanical and magnetic properties:
T-
A batch of 1,0 gram mixture containing Sm, SisN* (SiN^) and SiOj with the mo^ar ratio of Sm:SiNv3:Si02 corresponding to 7,33:5:5. The mixture was thoroughly | grinded in an argon filled glove box transferred to a niobium tube with one sealed end and heat treated in a graphite furnace in nitrogen atmosphere. The mixture was hi jated up to 1 75 0°C during two hours, held at this temperature for 22 hours and then | quenched to a temperature below the glass transition temperature by lowering th4 sample to the colder chamber of the graphite furnace. The sample was removed fjrom the furnace when it was cooled down to room temperature and 5 mm large piece^ wer
i
cut out for different analyses.
Scanning electron micrographs as well as X-ray powder diffraction patterns unambiguously showed a homogenous glass sample with no traces of crystalline I
!
phases. The EDX analysis of a carbon coated polished surface gave the following metal composition: 58(±1 sdv) at% Sm and 42(±1 sdv) at% Si. The O:N composition was assumed to be the same as found for the corresponding lanthanum containing glass, which would give an O:N ratio of 45:55. The O:N composition together wiith the metal composition gives a chemical stoichiometry of Sm^gSi^O^oNv^. The

refractivity index calculated from the measured Brewster angle was found to be 2,03(2), which corresponds to a Brewster angle of 63,8°. The hardness value obtained from the indentation experiments was 11,4 Gpa. The magnetic susceptibility measurements gave a paramagnetic signal and temperature dependence typical for Sm3+ containing samples. Sm3+ is a magnetic ion, thereby showing that high concentrations of the magnetic ions can be obtained. The susceptibility curve agreed well with the temperature dependent susceptibility found for Sm203.
Example 4, synthesis of tfac oxonitridoborosilicate with the nominal composition
A mixture of 1,5752 g La metal, 0,721 g Si02> 0,0468 g Si3N4 and 0,075 g BN was| thoroughly grinded in an argon filled glove box. The grinded mixture was transfenjed to a self made niobium crucible. The crucible was covered with para-film and transported to a graphite furnace for thermal treatment The graphite furnace was flushed with nitrogen gas three times before starting the heat treatment program, T sample was then heated to 1600°C during 2 hours, held at this temperature for 30 hours, tiie temperature was then raised to 1750°C and held at this ramp for 1 hour before quenching to a temperature below the glass transition temperature by lowering the sample to the colder furnace chamber. The sample was removed from tibe fuma|ce
i
when the room temperature was reached and 5 mm large pieces were cut out for different analyses.
Scanning electron micrographs as well as X-ray powder diffraction patterns unambiguously showed a homogenous glass sample with no traces of crystalline phases. The above mentioned analysis show clearly that the BN powder also was dissolved in the glass sample and is therefore integrated in the amorphous glass structure.
The results clearly shows that the physical and mechanical properties of oxide glasses such as hardness, elastic modulus, fracture toughness, and glass transition temperature

are improved/increased, when the atomic structure of the network is strengthened lj>y
replacing oxygen atoms by nitrogen atoms. Further, the results shows mat a very high
refractivity index could be achieved.
Further examples
i j
Chemical composition of investigated glasses is shown below. All compositions were melted at 1750°C for 22 hours. G indicates that glass is formed and C indicates that also a crystalline phase is present.
Chemical composition of investigated glasses is shown below. All compositions wjere
melted at 1500°C for 18 hours, and then increased the temperature at 1750°C for 30
min. and hold at this temperature for 30 min. and quenched to room temperature in a
cold chamber of furnace, under the flow of nitrogen gas.

Chemical composition of investigated glasses is shown below. All compositions wjere
melted at 1700 °C and 1200°C for 19.5 hours (the compositions were melted at 17(pO
i
°C for (2+12) hours and than at 1200 °C for 4 hours and than last run was done at 1700 °C for 1.5 hours). Basis of one gram. Partially glass is indicated when a glass phases is formed and some of the resulted material is crystalline. The crystals are incorporated in the glass mass. There is about 30-80 volume percent glass in the below mentioned synthesis examples.

Samples were melted at 1750°C for 30 hours, and then subsequently cool to roo temperature (inside of the furnace under the flow of N2).
KB. All above composition were melted in graphite holder (small in size) and samples
were inside of the Nb. Tube as well as during cooling N2 were insert through
lower\cold chamber instead of hot chamber.
Sample SmE3, SmP9, GdE3 and GdP9 were melted at 1750°C for 22 hours and
....
and GdA2 were melted at 1750°C for 30 hours, subsequently cool to room temperatlire
(inside of the furnace under the flow of Nj) See note.

NB. All above composition were melted in graphite holder (small in size) and samples were inside of the Nb tube, as well as during cooling N2 were insert through lower\cold chamber instead of hot chamber.
Samples were melted at 1750°C for 22 hours, subsequently cool to room temperahuje (inside of the furnace under the flow of N2) See note.

NB. All above composition were melted in graphite holder (small in size) and sarnp! les
i
were inside of the Nb tube3 as well as during cooling Nj were insert through !
lower\cold chamber instead of hot chamber.

We Claim:
1. A nitride glass having high refractivity index and good hardness values
with the general formula αxßyγz wherein
a is at least one electropositive element chosen from the group of alkali metals
Na, K and Rb, alkaline earth metals Be, Mg, Ca, Sr and Ba, transition metals
Zr, Hf Nb, Ta, W, Mo, Cr, Fe, Co, Ni, Zn, Sc, Y, Mn and La, main group
elements Pb, Bi, and f elements Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,
Yb, Lu, Th, Pa and U;
ß comprises Si and optionally at least one of the elements of the group of B, Ge,
Ga and Al; and
Y is N or N together with 02 whereby the atomic ratio of O:N is in the interval
from 65:35 to 0:100,
wherein the ratio α:ß is in the interval from 30:70 to 60:40, preferably in the
interval from 41:59 to 60:40,
wherein the ratio ß:γ is in the interval from 33:67 to 22:78.
2. A nitride glass as claimed in claim 1, wherein a is chosen from the group
of Lu, Mg, Y, Sc, Nd, Gd, Eu, Er, Tb, Tm, Dy, Yb, Th, Pa, Ca, Sr, Ba, La, Pr, Ce,
Sm, Mn and Ho.
3. A nitride glass as claimed in claims 1 and 2, wherein a is chosen from
the group of Ca, Sr, Ba, La, Pr, Ce, Sm, Mn and Ho.
4. A nitride glass as claimed in anyone of claims 1 to 3, wherein ß is Si.
5. A method for preparing a nitride glass as claimed in anyone of claims 1
to 4, comprising the steps of
a) mixing chemicals of the kind such as herein described corresponding to the desired composition of the kind such as herein described by using a as a pure metal and/or the corresponding metal nitrides or metal hydrides or any

other compound that transforms to the corresponding nitride in nitrogen atmosphere during the synthesis;
b) heating said compounds to at least 1000°C in the presence of nitrogen
gas, thereby obtaining a melt;
c) maintaining the temperature of step b) until the mixed chemical compounds
have formed a homogenous melt; and
d) cooling the melt to a temperature below the glass transition temperature and
using a cooling rate, that is sufficient in order to obtain a glass phase.
6. A method as claimed in claim 5, wherein the temperature in steps b) and c)
is above 1500 °C, and preferably above 1800 °C.
7. A nitride glass with the general formula wherein:
a is at least one electropositive element chosen from the group of alkali metals
Na, K and Rb, alkaline earth metals Be, Mg, Ca, Sr and Ba, transition metals
Zr, Hf Nb, Ta, W, Mo, Cr, Fe, Co, Ni, Zn, Sc, Y, and La, main group elements
Pb, Bi, and f elements Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th,
Pa and U;
P is chosen from at least one of the elements of the group comprising Si, B, Ge,
Ga and Al; and
Y is N or N together with O, whereby the atomic ratio of O:N is in the interval
from 65:35 to 0:100,
wherein the nitride glass is prepared by a method comprising the steps of;
a) mixing chemicals corresponding to the desired composition by using a as
a pure metal and/or the corresponding metal nit-ides or metal hydrides or any
other compound that transforms to the corresponding nitride in nitrogen
atmosphere during the synthesis;
b) heating said compounds to at least 1000 °C, preferably above 1500 °C,
and more preferably above 1800 °C, in the presence of nitrogen gas, thereby
obtaining a melt;
c) maintaining the temperature of step b) until the mixed chemical

compounds have formed a homogenous melt; and
d) cooling the melt to a temperature below the glass transition temperature
and using a cooling rate, that is sufficient in order to obtain a glass phase.

Documents:

3030-DELNP-2005-Abstract-(14-11-2008).pdf

3030-DELNP-2005-Abstract-19-05-2008.pdf

3030-delnp-2005-abstract.pdf

3030-DELNP-2005-Claims-(14-11-2008).pdf

3030-DELNP-2005-Claims-19-05-2008.pdf

3030-delnp-2005-claims.pdf

3030-DELNP-2005-Correspondence-Others-(14-11-2008).pdf

3030-DELNP-2005-Correspondence-Others-19-05-2008.pdf

3030-delnp-2005-correspondence-others.pdf

3030-delnp-2005-description (complete)-19-05-2008.pdf

3030-delnp-2005-description (complete).pdf

3030-DELNP-2005-Form-1-19-05-2008.pdf

3030-delnp-2005-form-1.pdf

3030-delnp-2005-form-18.pdf

3030-DELNP-2005-Form-2-19-05-2008.pdf

3030-delnp-2005-form-2.pdf

3030-delnp-2005-form-3.pdf

3030-delnp-2005-form-5.pdf

3030-DELNP-2005-GPA-19-05-2008.pdf

3030-delnp-2005-gpa.pdf

3030-delnp-2005-pct-409.pdf

3030-delnp-2005-pct-search report.pdf

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Patent Number

226212

Indian Patent Application Number

3030/DELNP/2005

PG Journal Number

01/2009

Publication Date

02-Jan-2009

Grant Date

11-Dec-2008

Date of Filing

06-Jul-2005

Name of Patentee

DIAMORPH AB

Applicant Address

ARRHENIUSLABORATORIET, STOCKHOLMS UNIVERSITET, SE-106 91 STOCKHOLM , SWEDEN

Inventors:

#	Inventor's Name	Inventor's Address
1	SAEID ESMAEILZADEH	VASTMANNAGATAN 49, SE-113 25 STOCKHOLM, SWEDEN

PCT International Classification Number

C03C 3/32

PCT International Application Number

PCT/SE2004/000034

PCT International Filing date

2004-01-14

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	0300056-9	2003-01-14	Sweden