Crystal Structure, Microstructure, and Microwave Dielectric Properties of MgGa2O4 and ZnGa2O4 Ceramics Prepared by a Reaction Sintering Method

The rapidly developing field of wireless communication technology requires advanced microwave dielectric ceramic materials. Here, spinel-structured MgGa2O4 and ZnGa2O4 ceramics were prepared using a reaction sintering method. The effect of sintering temperature was investigated with respect to the crystal structure, microstructure, and microwave dielectric properties of MgGa2O4 and ZnGa2O4 ceramics. Rietveld refinement analysis and quality factor (Q×f) values suggested that the occupancy sites and percentage of cations in MgGa2O4 would affect the microwave dielectric properties. Microstructure analysis indicated that abnormal grain growth at higher sintering temperatures would degrade the microwave dielectric properties of ZnGa2O4 ceramics. MgGa2O4 ceramics sintered at 1610°C exhibited promising microwave dielectric properties, i.e., εr = 9.4, Q×f = 167,500 GHz, and τf = −63 ppm/°C, while ZnGa2O4 ceramics sintered at 1550°C possessed a higher εr and a lower Q×f value of 10.5 and 126,900 GHz, respectively, and τf = −60 ppm/°C. The τf values of MgGa2O4 and ZnGa2O4 ceramics were tuned to near-zero levels by adding 8 mol.