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.