Effect of Sb-site nonstoichiometry on the structure and microwave dielectric properties of LiMgSbO ceramics

The non-stoichiometric Li3Mg2Sb1-xO6（0.05≤x≤0.125） compounds have been prepared via the mixed oxide method.The influences of Sb nonstoichiometry on the sintering behavior,microstructure,phase composition along with microwave dielectric performances for Li3Mg2Sb1-xO6 ceramics were studied.Combined with X-ray diffraction（XRD） and Raman spectra,it was confirmed that phase composition could not be affected by the Sb nonstoichiometry and almost pure phase Li3Mg2SbO6 was formed in all compositions.Appropriate Sb-deficiency in Li3Mg2SbO6 not only lowered its sintering temperature but also remarkably improved its Q×f value.In particular,non-stoichiometric Li3 Mg2Sb0.9O6 ceramics sintered at 1250℃/5 h owned seldom low dielectric constant εr=10.8,near-zero resonant frequency temperature coefficient τ_f=-8.0 ppm/℃,and high quality factor Q×f=86,300 GHz（at 10.4 GHz）.This study provides an alternative approach to ameliorate its dielectric performances for Li3Mg2 SbO6-based compounds through defect-engineering.