Microwave dielectric properties of aluminum substituted Ca0.61Nd0.26TiO3 ceramics

According the solid state reaction routine, Ca0.61Nd0.26Ti1−xAl4x/3O3 (x = 0, 0.05, 0.1, 0.15, 0.2) ceramics were synthesized and their microwave dielectric properties were determined. The X-ray diffraction results showed a single perovskite phase (JCPDS Card No. 01-082-0229) for 0 ≤ x ≤ 0.1. Dielectric constant (εr) decreased from 102.8 to 72.24, the Q×f value almost doubled, from 8560 to 15437 GHz, and the temperature coefficient of resonant frequency (τf) dropped from +247 to +155 ppm/°C. Then the X-ray diffraction patterns showed the appearance of secondary phase that degraded microwave dielectric properties of the system rapidly. At last, a ceramic possessing microwave dielectric properties of εr = 72.24, Q×f = 15437 GHz and τf = +155 ppm/°C could be obtained when sintered at 1400°C for 2 h in air, x = 0.1.