Microwave dielectric properties of (1 − x)Ca0.6La0.267TiO3 − xCa(Sm0.5Nb0.5)O3 ceramics

Microstructures and microwave dielectric properties of (1 − x)Ca0.6La0.267TiO3 − xCa(Sm0.5Nb0.5)O3 (0.1 ≤ x ≤ 0.7) ceramics have been investigated. A two-phase system was formed in the given compositional range. The grain morphology exhibited two different types of grain: large circular grain and small square grain. With the increasing x value, the grain morphology of the small square grain became irregular. The microwave dielectric properties were strongly related to the composition. As the x value increased from 0.1 to 0.7, the dielectric constant (ɛr) decreased from 87 to 48.3, the quality factor (Q × f) value from 14390 to 8360 GHz, and the temperature coefficient of resonant frequency (τf) value from +130.6 to −24.8 ppm/°C, respectively. For practical application, an ɛr of 74.3, a Q × f value of 12690 GHz and a τf value of +8.8 ppm/°C were obtained for 0.7Ca0.6La0.267TiO3−0.3Ca(Sm0.5Nb0.5)O3 ceramics sintered at 1450 °C for 4 h.