Low sintering temperature high permittivity ceramic composites for dielectric loaded microwave antennas

• Published in: Journal of materials science. Materials in electronics Vol. 26; no. 1; pp. 360 - 368
• Main Authors: Gu, F. F., Chen, G. H., Yuan, C. L., Zhou, C. R., Yang, Y.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01-01-2015; Springer Nature B.V
• Subjects: Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Dielectric properties; Dielectrics; Dopants; Firing; Materials Science; Microwaves; Optical and Electronic Materials; Permittivity; Sintering; Titanium dioxide; Microwave Dielectric Property; Sinter Temperature; TiO2 Content; BaCu; TiO2
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-014-2408-y

Compositions based on 0.2 Ca
0.8
Sr
0.2
TiO
3
–0.8Li
0.5
Sm
0.5
TiO
3
(CST–LST), suitable for microwave applications were developed by adding BaCu (B
2
O
5
) additives and TiO
2
dopant in order to tune the microwave dielectric properties and lower sintering temperature. Addition of BaCu (B
2
O
5
) lowered the firing temperature about 300 °C. A single solid solution phase with perovskite structure was formed through the entire compositions with BaCu (B
2
O
5
). The CST–LST ceramics with 5 wt% BaCu (B
2
O
5
) sintered at 950 °C exhibited the microwave dielectric properties of ε
r
 = 66.7, Q × 
f
 = 3,222 GHz, τ
f
 = −21.3 ppm/°C. Adding TiO
2
also improved the microwave properties. Typically, the CST–LST + 5 wt% BaCu (B
2
O
5
) + 1.5 wt% TiO
2
sintered at 950 °C showed ε
r
 = 71.6, Q × 
f
 = 3,441 GHz, τ
f
 = −10.8 ppm/°C. The high permittivity and low firing temperatures of BaCu (B
2
O
5
) added CST–LST ceramics with TiO
2
dopant can be ideal for the development of low cost ultra-small dielectrically loaded antennas. Compatibility with Ag electrode indicated that this material was suitable for low temperature co-fired ceramics.