Synthesis, Ion Mobility, and Phase Transition in the (NH4)6LiHf2Zr2F23 Compound

Abstract

Ion mobility and a phase transition (PT) in the compound (NH₄)₆LiHf₂Zr₂F₂₃ are studied using ¹H NMR, ¹⁹F NMR, XRD, and DSC methods. The types of ionic motions in the fluoride and ammonium sublattices of this compound are determined at 150–450 K; their activation energies are estimated. It is shown that an order-disorder PT occurs in this compound at 400–450 K to form a metastable high-temperature modification, where ionic motions are represented mainly by the diffusion of fluoride and ammonium ions.