Urusova, N.V.; Semkin, M.A.; Hoser, A.; Pirogov, A.N.: Features of Ni/Co ordering in the LiNi1-xCoxPO4 (x = 0.3, 0.5, 0.7) crystal structure. Journal of Surface Investigation 16 (2022), p. 847-853
10.1134/s1027451022050408
Abstract:
LiNi1–xCoxPO4 (x = 0.3, 0.5, 0.7) compounds have the olivine structure, space group Pnma, with 3d transition metal ions in the 4c octahedral position. The structural analysis of polycrystalline LiNi1 – xCoxPO4 (x = 0.3, 0.5, 0.7) samples is carried out by elastic neutron scattering, and variants of the mutual distribution of nickel and cobalt ions in the 4c position are studied in detail. For the LiNi0.5Co0.5PO4 compound, six options for the mutual distribution of nickel and cobalt ions are proposed. The best description of the neutron-diffraction patterns for the compounds with x = 0.5 is obtained for two models of the distribution of Ni and Co ions in the sequence: Ni–Co–Ni–Co and Co–Ni–Co–Ni, respectively. Nickel ions form planes in the LiNi0.5Co0.5PO4 sample, parallel to ab and alternating with cobalt planes. To describe the neutron-diffraction patterns of x = 0.3 and x = 0.7 compounds, four variants of models for the mutual distribution of Ni and Co ions in the 4c position are proposed. The four versions of the models considered lead to additional structural reflections that are absent in the experimental neutron-diffraction patterns. The experimental neutron-diffraction patterns of the LiNi0.7Co0.3PO4 and LiNi0.3Co0.7PO4 compounds can best be described using the equiprobable distribution of 3d transition-metal ions.