Crystal structure and enhanced microwave dielectric properties of non-stoichiometric Li3Mg2+xNbO6 ceramics

Non-stoichiometric Li3Mg2+xNbO6 ceramics were prepared by the solid-state reaction process. The effects of additional magnesium contents on the microstructure, sintering behavior and dielectric performance of Li3Mg2+xNbO6 ceramics were investigated systematically. XRD patterns and Rietveld refinement indicated that all of the samples exhibited a single-phase orthorhombic structure. The εr was dependent on the density and Q × f values were affected by the microstructure and density. Additionally, the τf values were related to the NbO6 octahedron distortion. Remarkably, the Li3Mg2.04NbO6 ceramics sintered at 1100 °C had outstanding microwave dielectric characteristics: εr = 16, Q × f = 140,000 GHz, τf = −5.6 ppm/°C, making these ceramics promising candidates for millimeter-wave applications.