Effect of Mn²⁺ substitution on the sintering behavior and microwave dielectric properties of Li₂Mg₁₋ₓMnₓSiO₄ ceramics

The effects of Mn²⁺ substitution on the sintering behavior and microwave dielectric properties of Li₂MgSiO₄ ceramics were systematically investigated. Li₂Mg₁₋ₓMnₓSiO₄ ceramics (x = 0–0.10) were prepared by a modified solid-state reaction method. X-ray diffraction combined with Rietveld refinement confirms that all samples retain a monoclinic Li₂MgSiO₄ structure (space group P2₁/c) without detectable secondary phases within the investigated composition range, indicating that Mn²⁺ successfully substitutes for Mg²⁺ in the lattice. Mn²⁺ substitution effectively reduces the optimum sintering temperature and promotes densification. The composition with x = 0.04 sintered at 1100°C for 1 h exhibits the highest relative density (96.42%) and the best microwave dielectric properties, with\({{\epsilon}}_{\text{r}}\)= 5.93 (measured at 13.179 GHz), Q×f = 34,845 GHz, and \({{\tau}}_{\text{f}}\) = −60.6 ppm/°C. SEM observations reveal that moderate Mn²⁺ substitution improves grain uniformity and densification, whereas excessive substitution leads to abnormal grain growth and degraded dielectric performance. Polarizability analysis further indicates that the increase in dielectric permittivity mainly originates from the enhanced intrinsic polarization induced by Mn²⁺ substitution. These results demonstrate that Mn²⁺ substitution is an effective strategy to improve the sintering behavior and optimize the microwave dielectric properties of Li₂MgSiO₄ ceramics.