Characterization and microwave dielectric properties of TiO2-modified 0.65CaTiO3–0.35Sm0.9Nd0.1AlO3 ceramics

Using various amounts of TiO2, the 0.65CaTiO3–0.35Sm0.9Nd0.1AlO3 ceramics were prepared via the conventional solid-state reaction method. The relationships between the crystalline structure and microstructure, as well as the microwave dielectric properties, were investigated. The sintered ceramics formed a solid solution, and short-range ordering at B-site ions was detected by Raman spectroscopy. A slight amount of Al-rich secondary phase was observed along the grain boundary, which increased with the TiO2 content. The additional TiO2 promoted the densification of ceramics and positively affected the dielectric constant, ɛr and the temperature coefficient of resonant frequency, τf. Nevertheless, the excess Al-rich secondary phase destroyed the short-range ordering of the B-site ions and deteriorated the Q × f value. Considering all three parameters of the microwave dielectric properties, the 0.25 wt% TiO2-modified 0.65CaTiO3–0.35Sm0.9Nd0.1AlO3 ceramic exhibited the best performance of ɛr = 40.43, Q × f = 51531 GHz and τf = −3.7 ppm/°C sintered at 1445 °C for 3 h.