Effects of LiF addition on sintering characteristics and microwave dielectric properties of wolframite structure ZnWO4 ceramics

Abstract To perform low-temperature sintering and achieve excellent microwave dielectric properties of ZnWO4 ceramics, LiF was selected as sintering additive. Composite ceramics were prepared by conventional solid-state reaction. Effects of LiF addition on sintering behavior, microstructural features, vibration characteristics, and microwave dielectric properties of ZnWO4 + x wt %LiF (0 ≤ x ≤ 6) ceramics were investigated via X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and complex bond valence theory. Results of microstructure and relative density revealed that using appropriate amount of LiF additive enabled one to effectively improve sintering characteristics. Partial substitution of F− for O2− ions caused alterations in interionic interaction, which resulted in that structural characteristics became internal factor affecting the performance. The relatively satisfactory dielectric characteristics (er = 15.943, Q × f = 36045 GHz, and τf = −69 ppm/°C) were detected in ceramics with x = 3, sintered at 900 °C, which was attributed to joint contribution of ionic substitution and the effect of secondary Li2WO4 phase.