Low-loss and ultra-low sintering temperature ceramics of AgCa1−xMgxVO4 (x = 0–0.09) for microwave applications

Pure and Mg-substituted AgCaVO4 compounds were explored using the conventional solid-state sintering method and their microwave dielectric properties were investigated. The XRD patterns indicate all samples belong to an orthorhombic structure with a space group of Pmna. The pure AgCaVO4 ceramic gives the dielectric properties: εr of 11.7, Q × f of 15,000 GHz, and τf of38 ppm/°C at 530 °C. The value of τf is correlated with the bond valence. In a limited range (x = 0.03–0.05), a small amount of Mg substitution can not only reduce the dielectric loss, but also increase the dielectric constant of the AgCa1−xMgxVO4 specimen. AgCa0.97Mg0.03VO4 ceramic sintered at 530 °C exhibits optimum properties of εr = 12, Q × f = 23,000 GHz and τf = –35 ppm/°C at microwave frequencies. The ceramic also shows good chemical compatibility with aluminum, providing a promising candidate for ULTCC applications.