Effect of Ga3+ substitution on the microwave dielectric properties of 0.67CaTiO3-0.33LaAlO3 ceramics

0.67CaTiO3-0.33La(Al1−xGax)O3 (0≤x≤0.4) (CTLAG) ceramics with pure perovskite structure were prepared by a conventional two-step solid-state reaction process. The effect of Ga3+ substitution for Al3+ on the microwave dielectric properties of the ceramics was subsequently investigated. As Ga content increased, the ionic polarizability increased and led to an increase of the dielectric constant (εr). Meanwhile, both the tolerance factor (t) of CTLAG ceramics and A-site bond valence were considered to have effect on the temperature coefficient of the resonant frequency (τf) with the increase of Ga content. Results also showed that the quality factor (Q×f ) varied with increasing Ga3+ content because of not only intrinsic factor but also extrinsic factors such as the bimodal grain size distribution, the variation of relative density, and the packing fraction. Excellent microwave dielectric properties with εr≈45.81, Q×f≈34,152 GHz, and τf≈3.09 ppm/°C were achieved for 0.67CaTiO3-0.33La(Al0.9Ga0.1)O3 ceramics sintered at 1420 °C for 4 h.