Discovery of the Li–Sr–La–Zr–O Compound and the Investigation of Its Lithium-Ion Conductivity

Single crystals of Li3.957Sr1.957La0.043ZrO6, having a new crystal structure, were successfully grown in air using the floating zone crystallization method. The obtained crystals were colorless and had a rectangular shape with a maximum dimension of 8(φ) × 50 mm. The elemental composition of the crystal was determined via energy-dispersive X-ray spectroscopy. Single-crystal X-ray structure analysis revealed that the crystal was monoclinic, in space group P21/n, with lattice parameters of a = 5.7506 (2) Å, b = 6.2968 (3) Å, c = 8.4906 (3) Å, and β = 97.066 (1) deg. Crystal structure refinement using 652 independent reflections resulted in a confidence factor (R) of 1.78% and a wR factor of 2.57%. The AC-impedance measurement revealed that the lithium-ion conductivity of the Li3.957Sr1.957La0.043ZrO6 single crystal at 298 K was 6.8 × 10-4 S/cm, and the activation energy calculated from the Arrhenius plot was 0.24 eV. The proposed single crystals exhibit significant potential for application as solid electrolytes for lithium-ion batteries at low temperatures.