The effects of strontium substitution, alumina addition and calcination temperature on the phase development and the microwave dielectric properties of BSSmT ceramics prepared by the conventional mixed oxide process with the nominal composition, (Ba1− x Srx)2Sm2Ti9O23 (x ≤ 0.07) were investigated. The phases synthesized upon calcination or sintering were analyzed by X-ray diffraction. It was found that the calcined powders were composed of (Ba,Sr)Sm2Ti4O12, Sm2Ti2O7 and (Ba,Sr)Ti4O9 phases, which converted to (Ba,Sr)Sm2Ti4O12 and (Ba,Sr)2Ti9O20 phases after pellets were sintered at the temperature from 1300 to 1350°C. Relative permittivity (ϵ r ) and the temperature coefficient of resonant frequency (τ f ) values were not much affected by the calcination temperature and Sr substitution, while the quality factor (Q·f) value was greatly influenced. It was also found that both strontium substitution for barium ions and alumina addition helped the formation of Ba2Ti9O20 secondary phase instead of BaTi4O9 secondary phase.
Acknowledgment
This work was supported in part by Grant No. R01-2003-000-11606-0 from the Basic Research Program of the Korea Science & Engineering Foundation.
Paper originally presented at IMF-11, Iguassu Falls, Brazil, September 5–9, 2005