Characterization on low loss dielectric Li2MgTiO4 ceramics based on chemical bond theory at microwave frequency

Abstract

The low loss microwave dielectric materials Li2MgTiO4 with rock salt structure were prepared by the modified solid state method. Sintering characteristics and microwave dielectric properties were investigated under various sintering temperatures ranging from 1200 °C to 1375 °C. The crystal structure was studied by the X-ray diffraction and the micro-structure was studied by the scanning electron microscopy (SEM) techniques. Rietveld refinement was used to analyze the structure of the crystalline phase. Based on the cell parameters, the bond ionicity, lattice energy, bond energy and coefficient of thermal expansion were calculated to evaluate the structural characteristics. The εr values could be strongly dependent on the bond ionicity of the TiO bond. The Q·ƒ values were affected by the lattice energy of TiO bonds. As for the τf values, it could be mainly affected by the coefficient of thermal expansion of LiO bonds. At the sintering temperature of 1350 °C, Li2MgTiO4 ceramics exhibited the excellent microwave properties of εr = 15.07, Q·ƒ = 97,629 GHz (at 8.2 GHz) and τf = −3.81 ppm/°C. These results demonstrated that Li2MgTiO4 ceramics could be promising candidate materials for the application of highly selective microwave ceramic resonators and filters.