Microstructure and Microwave Dielectric Properties of (1-x)SrTiO3-xLaAlO3 Ceramics

The (1-x)SrTiO3-xLaAlO3 (x = 0.3~0.6) microwave dielectric ceramics were prepared by two-step synthesis method. The effects of LaAlO3 content on the microstructure, microwave dielectric properties and crystal structure of (1-x)SrTiO3-xLaAlO3 ceramics were investigated. The results showed that the LaAlO3 powder prepared by coprecipitation method refines the ceramic grains, and the sintering temperature was reduced by about 100 deg C compared with the traditional solid phase method. In the studied composition range, a single tetrotetic solid solution was formed. With the increase of x, the unit cell volume decreases and the quality factor Q×f increases, but the dielectric constant epsilonr and resonant frequency temperature coefficient tauf both decrease. When x = 0.4, 0.6SrTiO3-0.4LaAlO3 ceramics get the best microwave dielectric properties at 1500 deg C for 4 h: epsilonr = 42.2, Q×f = 25643 GHz, tauf = 5.5 ppm / deg C.