The spinel structure was refined by using Rietveld full-profile analysis, together with X-ray and neutron powder diffraction data, and the compound was studied at high temperatures by means of differential scanning calorimetry and Raman spectroscopy. The electrical conductivity was measured in the high-temperature range. It was shown that the spinel structure underwent 2 successive order–disorder phase transitions, due to differing distributions of Li atoms and cation vacancies (,V) in a defect structure of NaCl-type: (Li)8a[Li0.33Ti1.67]16dO4 → [Li]16c[Li0.33Ti1.67]16dO4 → [Li1.330.67]16c[Ti1.670.33]16dO4. The low-temperature diffusion of Li occurred mainly via the mechanism … → Li(8a) → V(16c) → V(8a) → … in the spinel phase, or via the mechanism … → Li(16c) → V(8a) → V(16c) → … in an intermediate phase. In the high-temperature phase, the Li cations also migrated over 48f vacancies: … → Li(16c) → V(8a, 48f ) → V(16c) → …

Structure, Ionic Conduction and Phase Transformations in Lithium Titanate Li4Ti5O12. I.A.Leonidov, O.N.Leonidova, L.A.Perelyaeva, R.F.Samigullina, S.A.Kovyazina, M.V.Patrakeev: Physics of the Solid State, 2003, 45[11], 2183-8