Effect of Sb-site nonstoichiometry on the structure and microwave dielectric properties of Li3Mg2Sb1−xO6 ceramics

The non-stoichiometric Li 3 Mg 2 Sb 1−x O 6 (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 Li 3 Mg 2 Sb 1−x O 6 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 Li 3 Mg 2 SbO 6 was formed in all compositions. Appropriate Sb-deficiency in Li 3 Mg 2 SbO 6 not only lowered its sintering temperature but also remarkably improved its Q × f value. In particular, non-stoichiometric Li 3 Mg 2 Sb 0.9 O 6 ceramics sintered at 1250 °C/5 h owned seldom low dielectric constant ε r = 10.8, near-zero resonant frequency temperature coefficient τ f = −8.0 ppm/°C, 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 Li 3 Mg 2 SbO 6 -based compounds through defect-engineering.