Synthesis, characterization and microwave dielectric properties of spinel MgGa2O4 ceramic materials

Spinel MgGa2O4 ceramic materials were synthesized by solid-state method. MgGa2O4 powders were investigated with X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectrum, Raman spectrum, X-ray photoelectron spectrum (XPS), and high resolution transmission electron microscopy (HRTEM). The spinel-structured MgGa2O4 ceramics sintered at 1410 °C exhibited excellent microwave dielectric properties: a dielectric constant (ɛr) of 9.54, a quality factor (Q × f) of 117,000 GHz (at 14.7 GHz frequency) and a temperature coefficient of resonant frequency (τf) of −4.0 ppm/°C. MgGa2O4 ceramics have a wide sintering temperature region (∼150 °C) and nearly zero τf value. The large relative density, uniform microstructure and cation ordering resulted in high Q × f values. Crystal distortion from the oriented growth was advantageous to produce nearly zero τf value. MgGa2O4 ceramics are promising candidate materials for millimeter-wave devices.