Processing, phase analysis and microwave dielectric properties of Sr_5−xBi_xTi_1+xNb_4−xO₁₇ (x = 4, 3) ceramics

The ceramics in Sr_5−xBi_xTi_1+xNb_4−xO₁₇ (x = 4, 3) series were prepared using solid state sintering method. The phase and microwave dielectric properties were investigated. The parent phase Sr₂Bi₃Ti₄NbO₁₇ and SrBi₄Ti₅O₁₇ phases did not formed along the Sr_5−xBi_xTi_1+xNb_4−xO₁₇ series for the compositions with x = 3 and 4. The SrBi₄Ti₄O₁₅ phase formed as the major phase along with some secondary Bi₂Ti₂O₇ and SrTiO₃ phases for the composition with x = 4 in Sr_5−xBi_xTi_1+xNb_4−xO₁₇ series. For the composition with x = 3 in Sr_5−xBi_xTi_1+xNb_4−xO₁₇ series, Nb based Bi₂Ti₂O₇ pyrochlore phase formed as the major phase along with SrBi₃Ti₂NbO₁₂ phase as a secondary phase. In this study, good combination of microwaves dielectric properties i.e., ε_r ~ 166, Q_uf_o 8888 GHz and τ_f ~ 3.4 ppm/°C is obtained for the compositions with x = 4 sintered at 1200 °C and ε_r ~ 88, Q_uf_o~ 12,500 GHz and τ_f ~ − 9.36 ppm/°C is obtained for the composition with x = 3 sintered at 1200 °C.