Effect of Mn²⁺ substitution on phase composition, microstructure, and microwave dielectric properties of Zn_1.8-xMn_xSiO_3.8 ceramics

Microwave dielectric ceramics are essential for producing microwave components, seriously affecting the development and application of wireless communication technology. In this paper, Zn_1.8-xMn_xSiO_3.8 (0 ≤ x ≤ 0.20) ceramics were prepared by solid-phase reaction method. The sintering characteristics, phase compositions, microstructures, and dielectric properties of the materials were investigated. The addition of Mn²⁺ ions lowered the sintering temperature of the ceramics, and the densification temperature decreased from 1300 to 1200 ℃ as the amount of Mn²⁺ substitution increased. The Mn²⁺ substitution (x = 0–0.2) effectively formed a Zn₂SiO₄ solid solution without the appearance of any other secondary phases. A moderate amount of Mn²⁺ improves the microscopic morphology of Zn_1.8-xMn_xSiO_3.8 ceramics and enhances their Q × f. The theoretical and relative densities of the material were maximized at x = 0.04, where the ρ_bulk = 4.0865 g/cm³ and ρ_rela = 97.7%. At x > 0.12, the grain size grows, and anomalous grains appear and increase, deteriorating the microwave dielectric properties. The Q × f values are related to the microscopic morphology and packing fraction. α_obs increases from 13.360 to 13.596, the same trend as the α_theo, suggesting that ε_r is mainly affected by the ion polarizability. Among all the samples, the optimum microwave dielectric properties of Zn_1.76Mn_0.04SiO_3.8 ceramics were obtained by sintering at 1275 ℃ for 3 h:ε_r = 6.44(at 13.153 GHz), Q × f = 71,175.7 GHz,τ_f = − 50.7 ppm/℃. Due to its low dielectric constant and excellent quality factor, it will become the most promising electronic substrate material.