Li0.5−yNayLa0.5□Nb2O6 defect perovskite solid solutions with 0 ≤ y ≤ 0.5 were synthesized. Their structure was shown to undergo partial disordering with increasing sodium content. Lithium ion diffusion in the Li0.5−yNayLa0.5□Nb2O6 system exhibited no percolation effects. The ionic conductivity as a function of sodium content had a maximum due to two competing factors: the increase in perovskite cell volume and the decrease in lithium ion concentration.

Effect of Isovalent Substitution on the Structure and Ionic Conductivity of Li0.5 − yNayLa0.5□Nb2O6. A.G.Belous, O.N.Gavrilenko, O.I.Vyunov, S.D.Kobilyanskaya, V.V.Trachevskii: Inorganic Materials, 2011, 47[3], 308-12