Microwave Dielectric Properties of (Ba,Sr)O-Sm₂O₃-TiO₂ Ceramics

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, (Ba_{1− x} Sr_x)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.

Keywords:

• Microwave dielectric
• BSSmT ceramic
• dielectric resonator

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