Microstructural development of the La0.5Li0.5TiO3 lithium ion conductor processed by the laser floating zone (LFZ) method

Abstract

La2/3 − xLi3xTiO3 (0 < x < 0.17) compounds have reached great prominence in the last few years due to their high lithium ion conductivity. They present a perovskite-related structure (ABO3) with A-cation deficiency. However, neither the phase diagram nor the solidification processes are well known, which makes the growth of single crystals difficult. In this vein, we have processed La0.5Li0.5TiO3 polycrystalline powder by the LFZ method and studied the processed material by means of SEM, EDS, XRD and micro-Raman techniques. Three phases have been detected: the major phase (A) is a La–Li–Ti–O perovskite with 3x < 0.5, that forms large single crystal grains. Phase B is rutile TiO2 and appears as small precipitates surrounding phase A. Finally, we observe eutectic mixtures of phase A and a third phase (C) containing Ti and O in a ratio lower than 1∶2. Phase C is identified as a Li–Ti oxide, probably Li2Ti3O7.