Tunability of τf in garnet-structured Y3Ga5O12 microwave dielectric ceramics

The τ f of Y 3 Ga 5 O 12 ceramics was adjusted by Ca 2+ /Ti 4+ co-doping for Y 3+ at A-site and Ga 3+ at C-site to form Ca x Y 3- x Ti x Ga 5- x O 12 (0 ≤ x ≤ 2.0) ceramics by the solid-state reaction. When 0 ≤ x ≤ 1.7, all the samples remained as single garnet-structured with Ia- 3 d space group. The ε r increased from 10.4 ± 0.1 to 15.9 ± 0.1, and τ f optimized from −54.7 ± 1.0 to −8.3 ± 1.0 ppm/℃, attributing to the increase in polarizability per volume and “rattling” effect. Meanwhile, the Q × f slightly decreased from 98,200 ± 500 GHz to 65,300 ± 500 GHz due to the decrease in packing fraction. As x increased to 2.0, the properties dramatically deteriorated owing to the second phase CaTiO 3 . Optimal properties were obtained at x = 1.7, with ε r = 15.9 ± 0.1, Q × f = 65,300 ± 500 GHz and τ f = −8.3 ± 1.0 ppm/℃.