High quality factor of (Zn0.6Mg0.4)1.918GeO3.918 microwave dielectrics

The dependence of the microwave dielectric properties on the structural characteristics of (Zn1−xMgx)1.918GeO3.918 (0.2≤x≤0.6) was investigated. With increasing Mg2+ substitution up to x=0.4, the single-phase rhombohedral structure was detected, however, the secondary phase of Mg2GeO4 with orthorhombic structure was observed for further substitution of Mg2+. The quality factor (Qf) was dependent on the structural symmetry, in particular the tetrahedral distortion. (Zn0.6Mg0.4)1.918GeO3.918 showed the highest Qf value throughout the entire compositional range, which could be attributed to the high symmetry of the crystal structure with equilateral hexagonal rings composed of GeO4 and (Zn,Mg)GeO4 tetrahedra. The dielectric constant (K) and the temperature coefficient of resonant frequency (TCF) of the specimens changed only slightly up to x=0.4, while at x=0.5 and 0.6, they changed remarkably due to the formation of the secondary phase of Mg2GeO4.