Sodium Diffusion in Scheelite-Type Na2Zr(MoO4)3 and Na4Zr(MoO4)4

Complex sodium-containing oxides are of interest for the search and development of new materials for many practical applications. This paper presents the results of multiscale experimental and theoretical studies aimed to explore the mechanism of sodium-ion diffusion in the scheelite-related Na2Zr(MoO4)(3) and Na4Zr(MoO4)(4). These molybdates were synthesized by the precursor (formate) method. Ab initio modeling of sodium migration predicts a barrier of 1.0-1.2 eV for long-range sodium diffusion, which is confirmed by the impedance spectroscopy and the Na-23 NMR experiments. Our results allow us to assume the existence in Na4Zr(MoO4)(4) of an additional, much faster motional process (with energy barrier of 0.5-0.6 eV) associated with localized ion jumps.