Enhanced microwave dielectric properties of wolframite structured Zn1-xCuxWO4 ceramics with low sintering temperature

Abstract

The crystal structure, Raman vibration, chemical bond characteristics, and microwave dielectric properties of Zn1-xCuxWO4 (x = 0–0.15) ceramics prepared by a solid-state reaction were investigated by XRD refinement, Raman spectroscopy, P-V-L theory and XPS. According to the P-V-L theory, the properties of the W-O bond are stronger than those of the Zn-O bond, which makes a major contribution to the dielectric properties. The relative permittivity is mainly affected by the average bond ionicity, and the variations in the dielectric loss and τf are mainly attributed to the lattice energy and bond energy. XPS shows that the presence of Cu+ could produce oxygen vacancy defects, increasing the dielectric loss. Additionally, Raman spectra show that the increasing molecular polarizability causes the Raman shift to move to a low wavenumber, and the changes in Raman intensity and FWHM lead to a decrease in the degree of short-range ordering. Particularly, Zn0.97Cu0.03WO4 ceramics sintered at 925 °C showed satisfactory properties (εr = 14.20, tanδ = 1.473 × 10−4 at 9.087 GHz, and τf = −40 ppm/°C), which can potentially be applied to LTCC technology and indicate that Cu substitution can not only reduce the sintering temperature, but also optimize the dielectric properties.