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., ε_r = 9.4, Q×f = 167,500 GHz, and τ_f = −63 ppm/°C, while ZnGa₂O₄ 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 MgGa₂O₄ and ZnGa₂O₄ ceramics were tuned to near-zero levels by adding 8 mol.% CaTiO₃. These results indicate that MgGa₂O₄ and ZnGa₂O₄ ceramics produced by reaction sintering show promise for applications in the field of 5G communication.