Impacts of Al2O3 Doping on Microstructure, Phase Constitution and Microwave Dielectric Properties of Ca0.61Nd0.26TiO3 Ceramics

The effects of Al2O3 addition on microstructure, phase evolution and microwave dielectric properties of Ca0.61Nd0.26TiO3 – x mol Al2O3 (x = 0, 0.025, 0.05, 0.075, 0.1) ceramics have been investigated in this study. With x increasing from 0 to 0.05, the system maintained a single perovskite phase while bulk density decreased rapidly due to grain size degradation. Correspondingly, dielectric constant (ϵr) decreased from 103 to 79.2 and temperature coefficient of resonant frequency (τf) dropped from +247 to +159.3 ppm/°C. Moreover, anti-reduction of Ti4+ gave rise to a nearly doubled Q×f value, from 8600 to 15500 GHz. For 0.075≤x≤0.1, X-ray diffraction results showed a secondary phase whose peaks were consistent with Ca2Nb2O7 phase, resulting in decreased microwave dielectric properties.