Sintering behavior, structural evolution, and dielectric properties of Li2+MgTiO4F microwave dielectric ceramics

Abstract

Herein, the sintering behavior, structural evolution, microstructure, and dielectric properties of Li2+xMgTiO4Fx (0 ≤ x ≤ 5) ceramics were investigated. At x ≤ 0.75, Li2+xMgTiO4Fx ceramics formed a continuous solid solution with a cubic rock salt structure. Subsequently, a composite ceramic of Li2+xMgTiO4Fx and LiF was formed. It was found that the maximum mass percentage of LiF required to fully form a solid solution was between 11% and 13%. The Li2.75MgTiO4F0.75 exhibited the best dielectric properties: εr = 16.52, Q × f = 123,574 GHz, and τf = −18.11 ppm/°C. The substitution of F- for O2- resulted in a lower sintering temperature of 875 °C, which slightly suppressed the volatilization of Li, and thus optimized the dielectric properties. The decrease in lattice vibration damping behavior and the increase in electron cloud density resulted in lower dielectric losses. The reduction in molecular polarization rate led to a reduction in εr, and the increase in bond energy optimized τf. Good chemical compatibility with Ag electrode was demonstrated, indicating that Li2+xMgTiO4Fx ceramics have unlimited potential for LTCC applications.