Synthesis, structure and properties of lithium-ion conducting lanthanum niobates with defect perovskite structure

Chem. Met. Alloys 3 (2010) 90-95

https://doi.org/10.30970/cma3.0124

Anatolii G. BELOUS, Oksana N. GAVRILENKO, Sofiya D. KOBILYANSKAYA, Oleg I. V’YUNOV, Volodymyr V. TRACHEVSKII, Odile BOHNKE

Solid solutions with defect perovskite structure have been obtained in the system Li_0.5‑yNa_yLa_0.5Nb₂O₆ at 0 ≤ y ≤ 0.5. It has been shown that when sodium ions substitute for lithium ions, an increase in the unit cell volume of the defect perovskite is observed. The existence of lithium ions with different mobility in the system Li_0.5‑yNa_yLa_0.5Nb₂O₆ (0 ≤ y < 0.5) has been shown by ⁷Li NMR. A percolation mechanism of the Li ion diffusion is not observed in this system. The lithium-ion conductivity in Li_0.5‑yNa_yLa_0.5Nb₂O₆ (at y ≤ 0.43) is higher in comparison with La_0.5Li_0.5Nb₂O₆. This may be due both to the increased amount of more mobile Li⁺ ions in the sodium-substituted samples and to the increase of the cell volume. The lithium-containing lanthanum niobate La_0.5Li_0.5Nb₂O₆ has been obtained by the Pechini method. It has been shown that the resistance of this sample is lower than that of a sample of the same composition prepared by the solid-state reaction method.

Structure of the A-site deficient perovskite La_2/3_4/3Nb₂O₆ (space group Pmmm): La in position 1a (0 0 0), Nb in 2t (½ ½ z), O(1) in 1f (½ ½ 0), O(2) in 1h (½ ½ ½), O(3) in 2s (½ 0 z), O(4) in 2r (0 ½ z), and vacancies in 1c (0 0 ½).

Keywords

Sodium-containing lithium–lanthanum niobate/ Lithium ion mobility / Ionic transport / ⁷Li NMR / Pechini method