The doping-induced phase transition in rock salt-structured Li2Ti1−x(Mg1/3Ta2/3)xO3 (0 ≤x ≤ 0.4) ceramics revealed by EBSD and XRD refinement and its effects on the microwave dielectric properties

Abstract

The microwave dielectric properties (MDPs) of Li2TiO3-based ceramics can be effectively tailored by the doping-induced monoclinic-to-cubic transition. However, the mechanism of the effects of phase transition on the MDPs is still yet to be clarified, as it is hindered by overlap of the main diffraction peaks of the two phases. To solve this problem, we report accurate analyses of the phase composition of Li2Ti1−x(Mg1/3Ta2/3)xO3 ceramics by electron back-scattered diffraction (EBSD) mapping combined with X-ray diffraction (XRD) refinement. As the x value increases, the samples undergo a monoclinic-to-cubic transition, which leads to a decrease in εr, an increase in Q×f, and a negative shift of τƒ. Moreover, the theoretical values of εr, Q×f, and τƒ of the samples with various doping concentrations are calculated based on the phase composition analysis results. The theoretical values are consistent with the experimental data. The optimal MDPs (i.e., εr = 18.4, Q×f = 74300 GHz, and τf = 0.2 ppm/°C) are obtained in the sample with x = 0.2. The study results essentially reveal the effects of the doping-induced phase transition in Li2TiO3-based ceramic materials with a rock salt structure on the MDPs.