Phase evolution, structure and microwave dielectric properties of Li2+xMg3SnO6 (x=0.00-0.12) ceramics

In this study, the Li2+xMg3SnO6 (LxMS) ceramic systems were prepared by solid-state reaction using novel atmosphere-controlled sintering (x = 0.00-0.12). The influences of extra lithium contents on the phase evolution, crystal structure and microwave dielectric properties of Li2+xMg3SnO6 (LxMS) ceramics were systematically investigated. As samples were calcined from 800 to 1000 degrees C, the Li2+xMg3SnO6 phase was formed from the chemical reaction between Li2SnO3 and MgO phase. Pure Li2Mg3SnO6 phase could be observed for samples calcined at 1000-1100 degrees C. But when it was exposed to high temperature air over 1100 degrees C, the Li2+xMg3SnO6 decomposed into Mg2SnO4, MgO and Li2O. Because of the protective atmosphere and extra lithium, the epsilon(r) Qxf and tau(f) were significantly improved by the suppression of secondary phase and pores for 0.00 <= x <= 0.08. However, comprehensive microwave characteristics were deteriorated for 0.08<x <= 0.12, which were correlated with dielectric polarization, bond valence, FWHM, packing fraction and octahedral distortion. The excellent microwave characteristics of LxMS (x = 0.08) sintered at 1350 degrees C in novel controlled atmosphere were obtained. epsilon(r) = 12.7, Qxf = 168,330 GHz and tau(f) = 27.4 ppm/degrees C.