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

Spinel MgGa 2 O 4 ceramic materials were synthesized by solid-state method. MgGa 2 O 4 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 MgGa 2 O 4 ceramics sintered at 1410   °C exhibited excellent microwave dielectric properties: a dielectric constant ( ɛ r ) of 9.54, a quality factor ( Q   ×   f ) of 117,000   GHz (at 14.7   GHz frequency) and a temperature coefficient of resonant frequency ( τ f ) of −4.0   ppm/°C. MgGa 2 O 4 ceramics have a wide sintering temperature region (∼150   °C) and nearly zero τ f 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 τ f value. MgGa 2 O 4 ceramics are promising candidate materials for millimeter-wave devices.