Effects of Zn/Mg Ratio on the Microstructure and Microwave Dielectric Properties of (Zn1?xMgx)2SiO4 Ceramics

Ceramics of nominal composition (Zn_1−x Mg _x )₂SiO₄ were synthesized by the solid-state method. The phase evolution, microstructure, and microwave dielectric characteristics of the (Zn_1−x Mg _x )₂SiO₄ (0 < x < 1.0) ceramics were investigated systematically. The sintering range was widened and the densification temperatures of the present ceramics were much lower compared with the Zn₂SiO₄ and Mg₂SiO₄ end-members. Coexistence of Mg₂SiO₄ and Zn₂SiO₄ phases was observed in the (Zn_1−x Mg _x )₂SiO₄ ceramics with x = 0.4 and 0.6. The MgSiO₃ secondary phase was also observed due to Mg substitution. Changes in grain shapes from equiaxed to rectangular were observed in sintered samples as x varied from 0.7 to 1.0. The microwave characteristics of (Zn_1−x Mg _x )₂SiO₄ ceramics were significantly improved by the suppression of the MgSiO₃ phase, where an enhanced quality factor (Qf) value was obtained. The best microwave characteristics were achieved in the (Zn_1−x Mg _x )₂SiO₄ ceramic with Zn/Mg ratio of 1.5 sintered at 1250°C: ε _r = 6.2, Qf = 148,740 GHz, τ _f = −54.2 ppm/°C.