Effects of Ga2O3 doping on the microstructure and dielectric properties of SrTiO3-SmAlO3 ceramics for microwave applications

xSrTiO(3)-(1-x)SmAlO3 (ST-SA) (x = 0.4, 0.5, 0.6) microwave dielectric ceramics were prepared by solid-state reaction method and the microwave dielectric properties (E-r, Q x f, z(f)) were studied. The 0.4ST-0.6SA component with better Q x f and Gamma(f) was selected and the effects of different ywt % Ga2O3 (y = 0.5, 1.0, 1.5, 2.0, 2.5) doping on the phase structure, microstructure, and microwave dielectric properties of ceramics were investigated. X-ray diffraction analysis showed that Ga3+ mainly replaced Ti4+ site when y < 0.5, and when y > 0.5, Ga3+ start to replace Al3+ site. The best grain uniformity of the ceramics was observed at y = 2.0 by scanning electron microscopy testing. Raman spectroscopy shows that the stability of the oxygen octahedron is improved after Ga2O3 doping with increased Q x f value. The change of Ga2O3 doping amount also affects the dielectric properties of ST-SA ceramics. The optimum Q x f value of the ceramic is improved by about 50% from 10,278 GHz (7.465 GHz, 0.4ST-0.6SA) to 15,712 GHz (6.950 GHz, 0.4ST-0.6SA-2.0 wt% Ga2O3) with improved dielectric properties (Er = 36.14,zf = 4.17 ppm/degrees C).