Title of Invention	"A PROCESS FOR THE PREPARATION OF A NOVEL CERAMIC DIELECTRIC HAVING THE COMPOSITION BAO2-NB2O5-TIO2 USEFUL FOR MICROWAVE DIELECTRIC APPLICATION"
Abstract	A process for the preparation of a novel ceramic material having the composition Ba-Ti02 -Nb205/ useful for microwave dielectric application which comprises, (a) mixing oxides or carbonates of Barium, Niobium and Titanium dioxide, (b) grinding the mixture thoroughly to form a uniform reaction mixture, (c) calcining the resultant mixture in a crucible at a temperature in the range of 1000 to 1200°C, (d) cooling the reaction mixture, (e) grinding & compacting the resultant product to form powder, (f) sintering the resultant at a temperature in the range of 1200 to 1260°C.

Title of Invention

"A PROCESS FOR THE PREPARATION OF A NOVEL CERAMIC DIELECTRIC HAVING THE COMPOSITION BAO2-NB2O5-TIO2 USEFUL FOR MICROWAVE DIELECTRIC APPLICATION"

Abstract

A process for the preparation of a novel ceramic material having the composition Ba-Ti02 -Nb205/ useful for microwave dielectric application which comprises, (a) mixing oxides or carbonates of Barium, Niobium and Titanium dioxide, (b) grinding the mixture thoroughly to form a uniform reaction mixture, (c) calcining the resultant mixture in a crucible at a temperature in the range of 1000 to 1200°C, (d) cooling the reaction mixture, (e) grinding & compacting the resultant product to form powder, (f) sintering the resultant at a temperature in the range of 1200 to 1260°C.

Full Text	This invention relates to a process for the preparation of a novel ceramic material useful for microwave dielectric applications. With the progress in direct satellite broadcasting and cellular telephones, there has been an increasing demand for dielectric resonators. The versatality and adaptability of dielectric resonators to modern communication systems make them indispensable components for filters, oscillators, duplexers etc.(L.A.Trinogya; G.Kaizhou & I.e.Hunter, Practical Microstrip Circuit Design, Ellis Howard 1991). The dielectric resonators reduce the size of the components by a factor of Er where Er is the relative permittivitty of the material. The important characteristics required for a dielectric resonator are (1) high dielectric constant (25-100); (2) high unloaded quality factor and (3) small temperature variation of resonant frequency (Tf = 20 ppm/0C). Recently a few ceramic materials such as Ba Ti2 0 H.M.O'Bryan, J.Thomson, J.K.Plourde, J. Amer. Cer. Society, 57 (1974) 450); H.Sreemoolanadhan, J. Isaac, P.Koshy, M.T.Sebastian, K.A.Jose and P.Mohanan, Bri. Ceramic Trans. J. 94 (1995) 157); BaO-Nd2O3 -TiO2 (K.Wakino, K. Minia & H.Tamura, J. Amer. Ceram. Soc. 67(1984) 278; H.Sreemoolanadhan, M.T.Sebastian & P.Mohanan, Bri. Ceramic Trans. J. 95 (1996) In press): (Zr,Sn)TiO4 ( G. Wolfram and H.E. Goebel, Mater. Res. Bull. 30 (1995) 653) have been investigated. The main objective of the present invention is to provide a process for the preparation of a new ceramic material having high dielectric constant, high quality factor (low loss) and low temperature variation of resonant frequency. Another objective of the present invention is to provide a process for the preparation of new ceramic material. BaO-Ti02- 2Nb205 which is useful for microwave dielectric applications. The principle by which the invention is based on the reaction of the process of the invention is given below. BaC03 + Ti02 + 2IMb205 > BaTiNb4Oi3 + C02 Accordingly the present invention provides a process for the preparation of a novel ceramic material having the composition BaO-Ti02 -2Nb205 useful for microwave dielectric application which comprises, (a) mixing oxides or carbonates of Barium, Niobium and Titanium dioxide at 24:10:66 mol%, (b) grinding the mixture thoroughly to form a uniform reaction mixture, (c) calcining the resultant mixture in a crucible upto 10 hours at a temperature in the range of 1000 to 1200°C, (d) cooling the reaction mixture, (e) grinding & compacting the resultant product to form powder, (f) sintering the resultant upto 10 hours at a temperature in the range of 1200 to 1260°C. The mixture of the starting material is wet ground for a few hours say 2 to 4 hours in an agate mortar. The ground mixture is then transferred in to a crucible and calcined at temperature in the range of 1000 to 1200°C for a period in the range of 2 to 10 hours. The calcined powder is again ground well. The powder may be mixed with a binder and into desired compacts. The binder may be selected for increasing the cohesive nature of the powder. The amount of binder added may be from 2 to 5ml of 5% PVA (poly vinyl alcohol). The pressure used may be in the range of 100 to 200 MPa. The samples are then sintered at temperatures in the range 1200 to 1260 °C for 4 to 10 hours. The samples sintered at temperatures more than 1250 °C melted. The structure and microstructure of the samples were studied by x-ray diffraction and scanning electron microscopic techniques. The dielectric properties of the samples are studied in the microwave frequency region. The dielectric constant (Er) of the sample was measured by the post resonator method proposed by Hakki & P.O. Coleman IRE Trans. Microwave Theory Techn. MTT- 8 (1960)40) and modified by Courtney (W.E. Courtney, IEEE Trans. Microwave Theory & Techn. MTT-18 (1970)476). The unloaded quality factor was measured by the stripline method (APS Khanna & Y.Garault, IEEE Trans. Microwave Theory & Tech. MTT-31 (1983)261). This Q value is very close to .p!63that of a Dr used in a practical circuit(D.Kajfez & P.Guillon, Dielectric Resonators artech House Publishers, Massachusettus 1986). The measurements of dielectric constant and Qu are easly done automatically by a HP 8510 B Network Analyser with synthesizer (HP 8441B) and Reflection Transmission Test Unit (HP 3514B). Then the DR was slowly heated in the temperature range 25-80 C and the coefficient of thermal variation of resonant frequency (Tf) was obtained. The following examples are given to further illustrate the process of the present invention and therefore should not be construed to limit the scope of the present invention. Example 1 1.9734 gm of BaCO3 , 0.799 gm TiO2 and 5.316 gra Nb2O5 are weighed and mixed and ground well in an agate mortar for 1 hour. It is o then taken in platinum crucible and heated at 1240 C for 4 hours. The powder sample is cooled to room temperature. The sample is then ground well in an agate for 2 hours. It is then mixed with 2ml of binder Poly Vinyl alcohol(PVA) and is agian mixed well. The mixture is then shaped into cylindrical pellets of llmm diameter and 7mm height. The cylindrical compacts are o then kept on a platinum plate and sintered at 1255 c for 4 hours. The samples are then cooled to room temperature. Example 2 2.9601 gm of BaCO3 , 1.1985 gm TiO2 and 7.974 gm of Nb205 are weighed and mixed and ground well in an agate mortar for 2 hours. o It is the taken in a platinum crucible and heated at 1230 C for 6 hourss. The powder sample is then cooled to room temperature. The sample is then ground well in an agate for 3 hours. It is then mixed well with 3 ml of binder PVA and is again mixed well. The mixture is then shaped to into cylindrical pellets of 10mm diameter and 8mm height. The cylindrical compacts are then kept o on a platinum plate and sintered at 1260 C for 3 hours. The samples are then cooled to room temperature. The main advantages of the novel ceramic material prepared by the process of the present invention are : The BaO-TiO2 -2Nb205 ceramic material prepared by the process of the present invention has a high dielectric constant (Er=44+2), high unloaded quality factor(Qxf>25000) and low temperature variation of resonant frequency (Tf~16ppm/0C). These characteristics make the material a very useful for application as a Dielectric resonator in communication systems and as substrates in microwave integrated circuits. Compared to the use of alumina substrates the material prepared by the process of the invention decreases the size to about ha half not only for stripline resonators and filters but for all microwave circuits.S We Claim: 1. A process for the preparation of a novel ceramic material having the composition BaO-TiO2 - 2Nb205 useful for microwave dielectric application which comprises, (a) mixing oxides or carbonates of Barium, Niobium and Titanium dioxide at 24:10:66 mol%, (b) grinding the mixture thoroughly to form a uniform reaction mixture, (c) calcining the resultant mixture in a crucible upto 10 hours at a temperature in the range of 1000 to 1200°C, (d) cooling the reaction mixture, (e) grinding & compacting the resultant product to form powder, (f) sintering the resultant upto 10 hours at a temperature in the range of 1200 to 1260°C. 2. A process as claimed in claim 1 wherein the calcining is effected for a period in the range of 2 to 10 hrs. 3. A process as claimed in claims 1 & 2 wherein the sintering is effected for a period in the range of 4 to 10 hours. 4. A process for the preparation of a novel ceramic material having the composition Ba-Ti02 -2 Nb205, useful for microwave dielectric applications substantially as herein described with reference to the Examples.

Full Text

This invention relates to a process for the preparation of a novel ceramic material useful for microwave dielectric applications.
With the progress in direct satellite broadcasting and cellular telephones, there has been an increasing demand for dielectric resonators. The versatality and adaptability of dielectric resonators to modern communication systems make them indispensable components for filters, oscillators, duplexers etc.(L.A.Trinogya; G.Kaizhou & I.e.Hunter, Practical Microstrip Circuit Design, Ellis Howard 1991). The dielectric resonators reduce the size of the components by a factor of Er where Er is the relative permittivitty of the material. The important characteristics required for a dielectric resonator are (1) high dielectric constant (25-100); (2) high unloaded quality factor
and (3) small temperature variation of resonant frequency (Tf =

20 ppm/0C). Recently a few ceramic materials such as Ba Ti2 0
H.M.O'Bryan, J.Thomson, J.K.Plourde, J. Amer. Cer. Society, 57 (1974) 450); H.Sreemoolanadhan, J. Isaac, P.Koshy, M.T.Sebastian, K.A.Jose and P.Mohanan, Bri. Ceramic Trans. J. 94 (1995) 157);
BaO-Nd2O3 -TiO2 (K.Wakino, K. Minia & H.Tamura, J. Amer. Ceram. Soc. 67(1984) 278; H.Sreemoolanadhan, M.T.Sebastian & P.Mohanan,
Bri. Ceramic Trans. J. 95 (1996) In press): (Zr,Sn)TiO4 ( G.
Wolfram and H.E. Goebel, Mater. Res. Bull. 30 (1995) 653) have been investigated.
The main objective of the present invention is to provide a process for the preparation of a new ceramic material having high dielectric constant, high quality factor (low loss) and low temperature variation of resonant frequency. Another objective of the present invention is to provide a process for the preparation of new ceramic material. BaO-Ti02- 2Nb205 which is useful for microwave dielectric applications.
The principle by which the invention is based on the reaction of the process of the invention is given below.
BaC03 + Ti02 + 2IMb205 > BaTiNb4Oi3 + C02
Accordingly the present invention provides a process for the preparation of a novel ceramic material having the composition BaO-Ti02 -2Nb205 useful for microwave dielectric application which comprises,
(a) mixing oxides or carbonates of Barium, Niobium and Titanium dioxide at
24:10:66 mol%,
(b) grinding the mixture thoroughly to form a uniform reaction mixture,
(c) calcining the resultant mixture in a crucible upto 10 hours at a
temperature in the range of 1000 to 1200°C,
(d) cooling the reaction mixture,
(e) grinding & compacting the resultant product to form powder,
(f) sintering the resultant upto 10 hours at a temperature in the range of
1200 to 1260°C.

The mixture of the starting material is wet ground for a few hours say 2 to 4 hours in an agate mortar. The ground mixture is then transferred in to a crucible and calcined at temperature in the range of 1000 to 1200°C for a period in the range of 2 to 10 hours. The calcined powder is again ground well. The powder may be mixed with a binder and into desired compacts. The binder may be selected for increasing the cohesive nature of the powder. The amount of binder added may be from 2 to 5ml of 5% PVA (poly vinyl alcohol). The pressure used may be in the range of 100 to 200 MPa. The samples are then sintered at temperatures in the range 1200 to 1260 °C for 4 to 10 hours. The samples sintered at temperatures more than 1250 °C melted. The structure and microstructure of the samples were studied by x-ray diffraction and scanning electron microscopic techniques. The dielectric properties of the samples are studied in the microwave frequency region. The dielectric constant (Er) of the sample was measured by the post resonator method proposed by Hakki & P.O. Coleman IRE Trans. Microwave Theory Techn. MTT- 8 (1960)40) and modified by Courtney (W.E. Courtney, IEEE Trans.
Microwave Theory & Techn. MTT-18 (1970)476). The unloaded quality factor was measured by the stripline method (APS Khanna & Y.Garault, IEEE Trans. Microwave Theory & Tech. MTT-31 (1983)261). This Q value is very close to .p!63that of a Dr used in a practical circuit(D.Kajfez & P.Guillon, Dielectric Resonators artech House Publishers, Massachusettus 1986). The measurements of dielectric constant and Qu are easly done automatically by a HP 8510 B Network Analyser with synthesizer (HP 8441B) and
Reflection Transmission Test Unit (HP 3514B). Then the DR was
slowly heated in the temperature range 25-80 C and the coefficient of thermal variation of resonant frequency (Tf) was obtained.
The following examples are given to further illustrate the process of the present invention and therefore should not be construed to limit the scope of the present invention.
Example 1
1.9734 gm of BaCO3 , 0.799 gm TiO2 and 5.316 gra Nb2O5 are weighed

and mixed and ground well in an agate mortar for 1 hour. It is
o then taken in platinum crucible and heated at 1240 C for 4
hours. The powder sample is cooled to room temperature. The sample is then ground well in an agate for 2 hours. It is then mixed with 2ml of binder Poly Vinyl alcohol(PVA) and is agian mixed well. The mixture is then shaped into cylindrical pellets
of llmm diameter and 7mm height. The cylindrical compacts are
o then kept on a platinum plate and sintered at 1255 c for 4 hours.
The samples are then cooled to room temperature.
Example 2
2.9601 gm of BaCO3 , 1.1985 gm TiO2 and 7.974 gm of Nb205 are
weighed and mixed and ground well in an agate mortar for 2 hours.
o It is the taken in a platinum crucible and heated at 1230 C for 6
hourss. The powder sample is then cooled to room temperature. The sample is then ground well in an agate for 3 hours. It is then mixed well with 3 ml of binder PVA and is again mixed well. The mixture is then shaped to into cylindrical pellets of 10mm
diameter and 8mm height. The cylindrical compacts are then kept
o on a platinum plate and sintered at 1260 C for 3 hours. The
samples are then cooled to room temperature.
The main advantages of the novel ceramic material prepared by the process of the present invention are :
The BaO-TiO2 -2Nb205 ceramic material prepared by the process
of the present invention has a high dielectric constant
(Er=44+2), high unloaded quality factor(Qxf>25000) and low
temperature variation of resonant frequency (Tf~16ppm/0C). These
characteristics make the material a very useful for application as a Dielectric resonator in communication systems and as substrates in microwave integrated circuits. Compared to the use of alumina substrates the material prepared by the process of the invention decreases the size to about ha half not only for stripline resonators and filters but for all microwave circuits.S

We Claim:
1. A process for the preparation of a novel ceramic material having the
composition BaO-TiO2 - 2Nb205 useful for microwave dielectric application
which comprises,
(a) mixing oxides or carbonates of Barium, Niobium and Titanium dioxide at
24:10:66 mol%,
(b) grinding the mixture thoroughly to form a uniform reaction mixture,
(c) calcining the resultant mixture in a crucible upto 10 hours at a
temperature in the range of 1000 to 1200°C,
(d) cooling the reaction mixture,
(e) grinding & compacting the resultant product to form powder,
(f) sintering the resultant upto 10 hours at a temperature in the range of
1200 to 1260°C.

2. A process as claimed in claim 1 wherein the calcining is effected for a
period in the range of 2 to 10 hrs.
3. A process as claimed in claims 1 & 2 wherein the sintering is effected for a
period in the range of 4 to 10 hours.
4. A process for the preparation of a novel ceramic material having the
composition Ba-Ti02 -2 Nb205, useful for microwave dielectric applications
substantially as herein described with reference to the Examples.

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Patent Number

216517

Indian Patent Application Number

639/DEL/1996

PG Journal Number

13/2008

Publication Date

28-Mar-2008

Grant Date

14-Mar-2008

Date of Filing

27-Mar-1996

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH,

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	MAIJADIL THOMAS SEBASTIAN	REGIONAL RESEARCH LABORATORY, TRIVANDRUM 695019, INDIA.

PCT International Classification Number

C04B 35/46

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA