Effects of (Mg1/3Ta2/3)-substitution for Ti-site on the microwave dielectric properties of Li2MgTiO4 ceramics

Novel high quality factor microwave dielectric ceramics Li2MgTi1−x(Mg1/3Ta2/3)xO4 (0 ≤ x ≤ 0.5) were successfully prepared via a conventional solid-state ceramic route. The effects of isovalent substitutions (Mg1/3Ta2/3)4+ at the Ti-site on the sintering behaviors, microstructures, and microwave dielectric properties of Li2MgTiO4 ceramics were investigated in this paper. The sintered samples exhibited the single phase with cubic rock-salt structure belonging to Fm-3m space group in the whole composition range. Rietveld refinement which could be performed by the Fullprof program was taken to explain the effects of (Mg1/3Ta2/3)4+ ion substitution on the crystal structures of Li2MgTiO4 ceramics. With the (Mg1/3Ta2/3)4+ content increasing from 0 to 0.5, the quality factor Q·f firstly increased and decreased thereafter, while the dielectric constant εr almost linearly decreased. In addition, the τf values shifted to positive value with the amount of (Mg1/3Ta2/3)4+ increasing. The best composition appeared to be Li2MgTi0.6(Mg1/3Ta2/3)0.4O4, which showed excellent microwave dielectric properties of εr = 15.73, Q·f = 184,000 GHz and τf = − 12.54 ppm/°C. This made the Li2MgTi0.6(Mg1/3Ta2/3)0.4O4 ceramic a very promising candidate for use as a low-loss microwave material.