Microwave dielectric properties of (1−x)(Ca 0.88 Sr 0.12 )TiO 3 –x(Bi 0.5 Na 0.5 )TiO 3 high dielectric constant ceramics

(1−x)(Ca0.88Sr0.12)TiO3–x(Bi0.5Na0.5)TiO3 (CST–BNT, x = 0, 0.025, 0.05, 0.075, 0.10) high dielectric constant ceramics were prepared by the solid state reaction method, and the effects of (Bi0.5Na0.5)TiO3 (BNT) on the sintered properties, phase composition, microstructures, and dielectric properties of (Ca0.88Sr0.12)TiO3 (CST) ceramics were investigated as a function of the x-value and sintering temperature. The results showed that: BNT had no obvious influence on phase composition of CST ceramics, and the single phase solid solutions were obtained throughout the studied compositional range. Adding a moderate amount of BNT not only effectively lowered the sintering temperature from 1400 to 1275 °C, but also improved the sintered properties and the dielectric properties, especially that the τ f decreased from + 942 to + 639 ppm/°C, which was decreased by about 32%. For x = 0.05, the 0.95(Ca0.88Sr0.12)TiO3–0.05(Bi0.5Na0.5)TiO3 ceramics sintered at 1275 °C for 3 h exhibit an excellent combination of microwave dielectric properties: e r = 185.5, Q × f = 8116 GHz and τ f = + 639 ppm/°C, and which could be used as a promising candidate to equalize the materials with negative temperature coefficient of resonant frequency.