Structure analysis and microwave dielectric properties of germanium ion-doped ZnZrNb2O8 ceramics

Abstract

Germanium ion-doped ZnZrNb2O8 with composition of ZnZr1−xGexNb2O8 (x = 0.10, 0.20, 0.30, 0.35, 0.40) ceramics that exhibited improved Q × f value were first prepared by solid state method. X-ray diffraction (XRD) rietveld refinement was used to analyze the structure variations of the ceramic samples. The XRD patterns showed that all the samples contained the ZnZrNb2O8 phase with monoclinic structure. With the increase of germanium ion content, the dielectric constant decreased which was ascribed to the decrease of ionic polarizability. The improvement of Q × f value was mainly attributed to the increase of packing fraction. And, the emergence of the second phase also had a promoting effect to a certain extent. The temperature coefficient of resonant frequency (τ f ) correlated with the variation of bond valence of B-site. When x value exceeded 0.4, the microwave dielectric properties deteriorated seriously. The good combination microwave dielectric properties of e r = 23.7, Q × f = 89,341 GHz (where f = 8 GHz), and τ f = −65.48 ppm/°C were obtained for ZnZr1−xGexNb2O8 (x = 0.35) ceramics sintered at 1180 °C for 6 h.