Influence of Lithium Content on the Structure and Ionic Conductivity of Perovskite \(\mbox{La}_{(2/3) - x}\mbox{Li}_{3x}\mbox{TiO}_{3}\) Made by Double Mechanical Alloying Method

Abstract

Perovskite La\(_{(2/3) - x}\)Li\(_{3x}\)TiO\(_{3}\) samples with 0.06 \( \leq x \leq 0.15\) were prepared by a
double mechanical alloying method. Structure and Li$^{ + }$-ion conductive properties of the La\(_{(2 / 3) - x}\)Li\(_{3x}\)TiO\(_{3}\) samples were
investigated. Most of the analyzed perovskite samples exhibit a double unit cell. In these samples, a change of symmetry from tetragonal to orthorhombic is observed for sample with lithium content x = 0.06. Structural modifications were obtained mainly due to the cation vacancies ordering
along the c-axis, which disappeared gradually when the lithium content increased. At room temperature, the maximum values of grains and grain boundaries conductivities of the La\(_{(2 / 3) - x}\)Li\(_{3x}\)TiO\(_{3}\) samples were found to be of \(1.5\times 10$^{ - 3}\) S/cm and \(5.8 \times 10^{ - 5}\) S/cm, respectively. The temperature dependence of ionic
conductivity obeyed a non-Arrhenius behaviour. At temperature from 30 to 125\(^{\circ}\)C, the activation energy for grain and grain-boundary conductivity was found to be of $\sim $ 0.23 eV and $\sim $ 0.32 eV, respectively.