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 MgGa 2 O 4 and ZnGa 2 O 4 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 MgGa 2 O 4 and ZnGa 2 O 4 ceramics. Rietveld refinement analysis and quality factor ( Q × f ) values suggested that the occupancy sites and percentage of cations in MgGa 2 O 4 would affect the microwave dielectric properties. Microstructure analysis indicated that abnormal grain growth at higher sintering temperatures would degrade the microwave dielectric properties of ZnGa 2 O 4 ceramics. MgGa 2 O 4 ceramics sintered at 1610°C exhibited promising microwave dielectric properties, i.e., ε r  = 9.4, Q × f  = 167,500 GHz, and τ f  = −63 ppm/°C, while ZnGa 2 O 4 ceramics sintered at 1550°C possessed a higher ε r and a lower Q × f value of 10.5 and 126,900 GHz, respectively, and τ f  = −60 ppm/°C. The τ f values of MgGa 2 O 4 and ZnGa 2 O 4 ceramics were tuned to near-zero levels by adding 8 mol.% CaTiO 3 . These results indicate that MgGa 2 O 4 and ZnGa 2 O 4 ceramics produced by reaction sintering show promise for applications in the field of 5G communication.