Crystal structure, bond valence, thermal and microwave dielectric properties of Y3+xGa5-xO12 ceramics

To explore the effect of B-site ion variation in the garnet structure on the microwave dielectric properties, we introduced part of Y 3+ into Y 3 Ga 5 O 12 to form a series of Y 3 (Y x Ga 2- x )Ga 3 O 12 ( x  = 0–0.9) ceramics. Rietveld refinements, based on the XRD data, reveal that the Y 3+ x Ga 5- x O 12 ( x  = 0–0.8) ceramics crystallized in the garnet structure with the Ia -3 d space group, and two phases simultaneously coexisted in the x  = 0.9 ceramics. The average B-site cations were compressed, A-site cations exhibited rattling, and the overall structure of Y 3+ x Ga 5- x O 12 ( x  = 0–0.8) slightly expanded. As the concentration of Y 3+ at the B-site increased in pure-phase ceramics, the ε r (12.15–12.79) and τ f (−69.95 ∼ −60.72 ppm/°C) exhibited an upward trend, while the Q  ×  f descended (101,902–79,209 GHz). The factors influencing the microwave dielectric properties were further examined by considering the ionic polarizability, bond valence, lattice energy, and packing fraction.