Effect of MgO/La2O3 additives on sintering behavior and microwave dielectric properties of (Sr,Ca)TiO3-(Sm,Nd)AlO3 ceramics

The effect of MgO/La2O3 additives on phase composition, microstructures, sintering behavior, and microwave dielectric properties of 0.7(Sr0.01Ca0.99)TiO3−0.3(Sm0.75Nd0.25)AlO3 (7SCT-3SNA) ceramics prepared via conventional solid-state route were systematically investigated. MgO/La2O3 as additives showed no obvious influence on the phase composition of the 7SCT-3SNA ceramics and all the samples exhibited pure perovskite structures. The presence of MgO/La2O3 additives effectively reduced the sintering temperature of 7SCT-3SNA ceramics due to the formation of a liquid phase at a relatively low temperature during sintering progress. The 0.5 wt% MgO doped 7SCT-3SNA sample with 0.5 wt% of La2O3, sintered at 1320 °C for 4 h, was measured to show superior microwave dielectric properties, with an εr of 45.57, a Q×f value of 46205 GHz (at 5.5 GHz), and τf value of −0.32 ppm/°C, which showed dense and uniform microstructure as well as well-developed grain growth.