Effect of Cu2+ substitution on phase composition, microstructure, and microwave dielectric properties of Mg1−xCuxSiO3 ceramics

Abstract

Solid-state sintering method was used for the synthesis of Mg_1−xCu_xSiO₃ (x = 0–0.06) ceramics.The phase, microstructure and microwave dielectric properties of ceramics were studied.MgSiO₃ exists in polycrystalline form and is composed of orthorhombic MgSiO3 as the main phase, SiO₂ and monoclinic MgSiO₃ as the secondary phase. The existence of the secondary phase will deteriorate the sintering characteristics and dielectric properties. Appropriate Cu²⁺ substitution can effectively eliminate SiO₂ phase at relatively low temperature, and inhibit the formation of monoclinic MgSiO₃ phase. The substitution of Cu²⁺ improves the sintering properties of MgSiO₃ ceramic significantly, the maximum relative density increased from 92.3% at x = 0 to 96.58% at x = 0.02, and the sintering temperature decreased by 50℃. With the increase of Cu²⁺ content, the lattice parameters also increase. Dielectric constant is mainly affected by density and intrinsic polarizability, and Q × f is influenced by the microstructure, density and secondary phase content. When the x content increases from 0 to 0.02, the Q × f value of Mg_1−xCu_xSiO₃ increases from 27,378 GHz to 87,283 GHz. The resonant frequency temperature coefficient of the ceramic is also corrected. For x = 0.02 composition (Mg_0.98Cu_0.02SiO₃) sintered at 1420℃ for 3 h, good dielectric properties were obtained at 13.565 GHz:( ε_r = 6.58, Q × f = 87,283 GHz and τ_f =  − 11.8 ppm/°C). Due to its low dielectric constant and excellent quality factor, it is very suitable for high-frequency communication applications.