Crystal growth of La_2/3- Li₃ TiO₃ by the TSFZ method

Double-perovskite-type La_2/3- Li₃ TiO₃ (LLT) crystals were grown by the travelling solvent floating zone (TSFZ) method. When the floating zone (FZ) crystal growth method was applied, the La₂Ti₂O₇ phase was deposited as an inclusion in the initial growth region. Using the TSFZ crystal growth method, however, inclusion-free LLT crystals were obtained for a 10 mol% La₂Ti₂O₇-poor composition solvent relative to the stoichiometric LLT crystals. The molten zone was initially unstable as a result of habit plane formation during the crystal growth; however, the molten zone was stably maintained for a long period of time by decreasing the feed rate compared with the growth rate. Hence, LLT crystals of approximately 5 mmφ and 37 mm in length were obtained. The anisotropic ionic conductivity of the crystals annealed in air was σ[110]/σ[001] ≈ 3, with σ[110] = 1.64 × 10^-3 S cm^-1 and σ[001] = 5.26 × 10^-4 S cm^-1. LLT single crystals are candidates for high-performance solid-state electrolytes in all-solid-state Li ion batteries.