Investigation and characterization on crystal structure and enhanced microwave dielectric properties of non-stoichiometric Li3+xMg2NbO6 ceramics

Abstract

Non-stoichiometric Li3+xMg2NbO6 (x = 0 −0.08) microwave dielectric ceramics with ultra-low loss were synthesized through the solid-state reaction process. The effects of additional lithium contents on the microstructure, sintering behavior, structural characteristics and microwave dielectric properties were studied detailedly. Based on Rietveld refinement, the relation between crystal structure and microwave dielectric properties was investigated according to the structural characteristics such as the polarizability, packing fraction and NbO6 octahedron distortion. The ɛr depended on the polarizability. The Q × f was determined by the average grain size and packing fraction. Additionally, the NbO6 octahedron distortion affected the τf values. Particularly, Li3+xMg2NbO6 (x = 0.04) composition possessed extraordinarily excellent microwave dielectric properties: εr= 15.8, Q × f = 150,000 GHz (9.85 GHz), τf = −29 ppm/°C, which made the ceramics as promising candidates for millimeter-wave applications.