Synthesis and ionic conductivity of LixLa(1−x)/3Nb1−yTayO3 solid solutions

In this study, solid solutions of double-perovskite-type LixLa(1−x)/3Nb1−yTayO3 (x = 0.1, y = 0.0–1.0) were synthesized by solid-state reaction. We successfully prepared tetragonal Li0.1La0.3Nb1−yTayO3 single phases by increasing the reaction temperature and the Ta composition. The lattice constants of Li0.1La0.3Nb1−yTayO3 were observed to increase with increasing Ta composition, and densified Li0.1La0.3Nb1−yTayO3 pellets composed of larger grains than Li0.1La0.3NbO3 and Li0.1La0.3TaO3 were obtained. The relationship between the Nb–Ta solid solution in Li0.1La0.3Nb1−yTayO3 and ionic conductivity was investigated, which revealed that Li0.1La0.3Nb1−yTayO3 (y = 0.2) exhibited maximum ionic conductivity (σ = 7.78 × 10−5 S cm−1) at room temperature and that ionic conductivity decreased with increasing Ta composition. The activation energies of Li0.1La0.3Nb1−yTayO3 were found to be 0.34–0.38 eV and increased with increasing Ta composition.