Effect of Li concentration on the ionic conductivity of Li_xLa_(1−x)/3Nb_0.80Ta_0.20O₃ solid solutions

抄録

In this study, we successfully synthesized Li_xLa_(1−x)/3Nb_0.80Ta_0.20O₃ solid solutions with different Li concentrations (x = 0.00–0.30) by a solid-state reaction. With an increase in x, the crystal structure of Li_xLa_(1−x)/3Nb_0.80Ta_0.20O₃ initially changed from orthorhombic (0.00 ≤ x ≤ 0.05) to tetragonal (0.10 ≤ x ≤ 0.25) and then from tetragonal to cubic (x = 0.30). Grain sizes of Li_xLa_(1−x)/3Nb_0.80Ta_0.20O₃ increased with an increase in x. Moreover, densified Li_xLa_(1−x)/3Nb_0.80Ta_0.20O₃ pellets were obtained. Li_xLa_(1−x)/3Nb_0.80Ta_0.20O₃ with x = 0.10 showed the highest ionic conductivity of 7.78 × 10⁻⁵ S cm⁻¹ at room temperature, which decreased with an increase in x from 0.10 to 0.30. Activation energies of Li_xLa_(1−x)/3Nb_0.80Ta_0.20O₃ were in the range of 0.31–0.38 eV, which increased with an increase in x.