The effect of Ga3+ addition on the sinterability and microwave dielectric properties of RE3Al5O12 (Tb3+, Y3+, Er3+ and Yb3+) garnet ceramics

The RE3Al5O12 (RE=Tb, Y, Er, Yb) ceramics have been prepared by the mixed oxide route and the influence of Ga3+ doping on their properties is investigated. The intrinsic Y3Al5O12 (YAG) ceramic sintered at 1650 °C for 4 h showed good dielectric properties; (εr=10.1, Qu×f=65,000 GHz, τf=−45 ppm/°C). Addition of Ga2O3 was found to be beneficial in improving the densification of Tb3Al5O12, Er3Al5O12 and Yb3Al5O12 except Y3Al5O12 where Nb2O5 is the better choice. Among Ga3+ added samples, the composition Yb3Al5O12+1 wt% Ga2O3 showed good microwave dielectric properties: εr=10.3, Qu×f=50,000 GHz, τf=−58 ppm/°C. The Y3Al5O12 doped with 1 wt% Nb2O5 has εr=10.7, Qu×f=120,000 GHz and τf=−45 ppm/°C. The ceramics have good thermal properties (CTE=2–3 ppm/°C, λ=2–12 W/m K).