Microstructure and microwave dielectric properties of (Zn_1−x Mg _x )₂SiO₄ ceramics

Abstract

(ZnMg)₂SiO₄ powders was prepared by the sol-gel process, and the microstructure and dielectric properties of (Zn_1−xMg_x)₂SiO₄ microwave materials were investigated systematically. TG-DSC and XRD analyzes for gels indicate that the (ZnMg)₂SiO₄ with pure willemite phase could be obtained at low temperature of 850°C. Further, XRD illustrates that just small amounts of Mg can be incorporated into Zn₂SiO₄ lattice, and the solid solution limit of Mg in Zn₂SiO₄ is about x = 0·1. By appropriate Mg substitution for Zn, the sintering range is widened and the sintering temperature of Zn₂SiO₄ ceramics can be lowered effectively. SEM shows that Mg-substitution for Zn can promote the grain growth of Zn₂SiO₄. Moreover, the microwave dielectric properties strongly depended on the substitution content of Mg and sintering temperatures. (Zn_0·8Mg_0·2)₂SiO₄ dielectrics sintered at 1170°C show the condense microstructure with small uniform grains and best microwave properties: ɛ _r = 6·3, Q × f = 189800 GHz and τ _f = −63 ppm/°C.