Enhanced Microwave Dielectric Properties in Mg2Al4Si5O18 Through Cu2+ Substitution

Abstract

AbstractThe Mg2Al4Si5O18 ceramic is considered as a kind of important candidates for millimeter‐wave applications. In this work, Mg2–xCuxAl4Si5O18 (0≤x≤0.16) ceramics were synthesized by solid‐state reaction, aiming to improve the microwave dielectric properties. According to the X‐ray powder diffraction (XRD) analysis, Cu2+ ions enter into the Mg2Al4Si5O18 lattice and form a solid solution. The dense microstructure was observed in the Cu‐substituted Mg2Al4Si5O18 ceramics at x=0.04 sintered at 1420 °C. The dielectric constant (ϵr) values depend on the microstructure, secondary phase and ionic polarizability of the samples. The quality factor (Qf) values are dominated by the microstructure, secondary phase and centro‐symmetry of [Si4Al2] hexagonal ring. The temperature coefficients of resonance frequency (τf) are strongly related to the Mg/Cu−O bond valance. In comparison to pure Mg2Al4Si5O18 ceramics, the excellent microwave dielectric properties with ϵr=4.56, Qf=31,100 GHz and τf=−52 ppm/°C were obtained at x=0.04 with sintering at 1420 °C. Thus, the Mg2–xCuxAl4Si5O18 (0≤x≤0.16) ceramics will be promising millimeter‐wave communication materials.