Synthesis, structure, ion mobility, phase transitions, and ion transport in rubidium ammonium hexafluorozirconates

Rubidium ammonium hexafluorozirconates Rb2−x (NH4)x ZrF6 (1.5 < x < 2.0) have been synthesized, and their structure, ion mobility (180–480 K), and electrophysical properties have been studied by X-ray crystallography, 1H and 19F NMR, DTA, and impedance methods. Compounds with x > 1.5 are isostructural with (NH4)2ZrF6. Rubidium cations are isomorphously substituted for the ammonium cations. The high-temperature modifications of the compounds, which form upon the phase transitions at 413–418 K, are characterized by translational diffusion of ions in the fluoride and ammonium sublattices. The 19F NMR spectra are characterized by uniaxial 19F magnetic shift anisotropy. The electrophysical properties of this series of compounds are studied in the temperature range 300–480 K.