Synthesis, Microstructure, and Microwave Dielectric Properties of Spinel ZnGa2O4 Ceramics

Spinel ZnGa 2 O 4 ceramics were synthesized by conventional solid-state method and their microwave dielectric properties were investigated. The phase evolution and microstructures of specimens were studied by XRD and SEM. The textured surface microstructures of ZnGa 2 O 4 ceramics formed at high sintering temperatures. The spinel-structured ZnGa 2 O 4 ceramics sintered at 1385°C exhibited excellent microwave dielectric properties: a dielectric constant (ε r ) of 10.4, a quality factor ( Q × f ) of 94.600 GHz, and a temperature coefficient of resonant frequency (τ f ) of −27 ppm/°C. ZnGa 2 O 4 ceramics have a low sintering temperature, a wide temperature region, and a small negative τ f value. They are promising candidate materials for millimeter-wave devices.