Synthesis, Crystal Structure, and Stability of Cubic LiLaZrBiO.

Li oxide garnets are among the most promising candidates for solid-state electrolytes in novel Li ion and Li metal based battery concepts. Cubic LiLaZrO stabilized by a partial substitution of Zr by Bi has not been the focus of research yet, despite the fact that Bi would be a cost-effective alternative to other stabilizing cations such as Nb and Ta. In this study, LiLaZrBiO (x = 0.10, 0.20, ..., 1.00) was prepared by a low-temperature solid-state synthesis route. The samples have been characterized by a rich portfolio of techniques, including scanning electron microscopy, X-ray powder diffraction, neutron powder diffraction, Raman spectroscopy, and Li NMR spectroscopy. Pure-phase cubic garnet samples were obtained for x ≥ 0.20. The introduction of Bi leads to an increase in the unit-cell parameters. Samples are sensitive to air, which causes the formation of LiOH and LiCO and the protonation of the garnet phase, leading to a further increase in the unit-cell parameters. The incorporation of Bi on the octahedral 16a site was confirmed by Raman spectroscopy. Li NMR spectroscopy shows that fast Li ion dynamics are only observed for samples with high Bi contents.