M.M. Polyantsev

Ionic mobility and phase transitions in heptafluorodiantimonates MSb2F7 and Cs(1−x)Mx′Sb2F7 (M′ = K, NH4) according to NMR and DSC data

Ionic mobility and phase transitions in heptafluorodiantimonates with homo- and heteroatomic cations in the systems MSb2F7 (M = K, Cs, NH4) and CsM’Sb2F7 (M’ = K, NH4) have been studied using the 19F, 1H NMR and DSC methods. Analysis of the 19F and 1H NMR spectra made it possible to reveal the nature of ion motions in the fluoride and proton sublattices upon temperature variation and to determine the types and temperature ranges of such motions. It was found that diffusion of fluorine ions becomes the dominant form of ion motions in the high-temperature modifications, the amount of diffusing ammonium ions depending on the composition of a sample. The observed phase transitions in cesium-potassium and cesium-ammonium fluoroantimonates(III) leading to the formation of high-temperature modifications are the transitions to superionic state. According to preliminary results of electrophysical studies, hightemperature phases Cs1−x(NH4)xSb2F7 (0.05 ≤ x ≤ 0.6) are superionic, their conductivity reaching −10−3-10−4 S/cm at 463–483 K.

Ion mobility and conductivity in solid solutions in the KBiF4–ZrF4 system

The ion mobility and conductivity in solid solutions with the fluorite structure (100–x)KBiF4 + xZrF4, where x = 2.5–15 mol %, is studied by the methods of differential scanning calorimetry (DSC), X-ray diffraction (XRD), and 19F NMR. The character and type of ion transport in the fluorite sublattice of solid solutions are studied as well as the temperature intervals in which it is observed (150–570 K). For solid solutions containing 5 and 10 mol % ZrF4, the fluorine ion diffusion coefficient is assessed. It is found that the conductivity in the solid solution systematically decreases as the content of zirconium tetrafluoride in the sample decreases, which is probably due to the formation of strongly bound complexes formed by interstitial fluoride ions with zirconium cations. The presence of the high ionic conductivity in the tested solid solutions (from ~10–3 to 10–2 S/cm) makes this material a good candidate for preparation of materials with the high ion-conducting properties.

Ion mobility and phase transitions in the compounds K0,65Rb0,35SbF4 and (NH4)0,4Rb0,6SbF4 from NMR and DSC data

The NMR and DSC methods are used to study ion mobility and phase transitions in crystalline phases of K0,65Rb0,35SbF4 (I) and (NH4)0,4Rb0,6SbF4 (II). Their 19F and 1H NMR spectra are analyzed to trace the patterns of ion motions in the fluoride and ammonium sublattices at temperatures of 150–500 K and determine the types of motions and the corresponding temperature ranges. The phase transition in compound I is found to lead to a modification in which the dominant type of ion motions is the diffusion of fluoride ions. It is suggested that compounds I and II should demonstrate a conductivity of ≈10−4–10−2 S/cm at temperatures above 450 K.

Thermal and Transport Properties, Ion Mobility, and Phase Transitions in Compounds (NH 4 ) 6 CsZr 4 F 23 and (NH 4 ) 6 CsHf 4 F 23

Thermal, electrophysical properties, ion mobility, and phase transitions (PT) in compounds (NH4)6CsZr4F23 (I) and (NH4)6CsHf4F23 (II) have been studied by 1H, 19F NMR, X-ray powder diffraction, DSC, and impedance spectroscopy. The types of ion motions in the fluoride and ammonium sublattices of both compounds have been determined in temperature range 150–450 K and their activation energy has been assessed. Phase transitions in compounds I and II has been revealed in temperature range 380–404 and 384–412 K to form high-temperature modifications with diffusion of fluoride and ammonium ions as the main type of ion motions. The high ionic conductivity of compounds I and II (higher 10–4 S/cm at 463 K) allows one to refer these fluoro complexes to the class of superionic conductors.

Synthesis and Ion Mobility in Glasses of ZrF 4 –BiF 3 –Rb(Cs)F Fluoride Systems

A new procedure has been suggested for the synthesis of bismuth fluorozirconate glasses in the ZrF4–BiF3–MF systems (M = Rb, Cs), which is based on the use of the relatively moisture-resistant Rb2ZrF6 and Cs2ZrF6 fluorides rather than extremely hygroscopic rubidium and cesium fluorides. The types of ion motions, trends in ion mobility dynamics, and factors determining this dynamics as a function of the glass composition have been elucidated. A rather high ionic conductivity of glasses above 470 K, σ ≥ 10–4 S/cm, makes them promising candidates for use in design of functional materials.

Ion Mobility In Complex Antimony(III) Sulfate Fluorides M6Sb4(SO4)3F12 (M = Rb, Cs, NH4) and (NH4)2Sb(SO4)F3 According to 19F and 1Н NMR Data

Abstract19F and 1Н NMR methods were used to study ion mobility in M6Sb4(SO4)3F12 (M = Rb, Cs, NH4) and (NH4)2Sb(SO4)F3 complex antimony(III) sulfate fluorides with alkali cations and ammonium. The types of ionic mobility in these compounds were identified at 150–470 K.

Ionic mobility and conductivity in PbSnF4 doped with CaF2 from the NMR and impedance spectroscopy data

The ionic mobility and conductivity in the crystalline phases of PbSnF4–xCaF2 systems (x = 2.5 mol.%, 5 mol.%, 7.5 mol.%, and 10 mol.%) in the temperature range of 150-500 K are studied by NMR and impedance spectroscopy. The parameters of 19F NMR spectra, types of ion motions, and ionic conductivity in the PbSnF4 compound doped with calcium fluoride are found to be determined by the temperature and concentration of calcium fluoride. The specific conductivity of the crystalline phases in the PbSnF4–CaF2 systems is rather high at room temperature, and hence, one cannot exclude the possibility to use them for the creation of functional materials with a high ionic (superionic) conductivity.

Phase transitions and ionic mobility in solid solutions in the BiF3–KF–ZrF4 system

The phase transitions and ionic mobility in solid solutions (SS) with the fluorite structure ((100–х)KBiF4–xZrF4, where х = 2.5-10 mol.%) are studied by DSC, X-ray crystallographic analysis, and 19F NMR methods. Phase transitions are determined in the solid solutions containing 10% of ZrF4. The types of ion motions in the SS fluoride sublattice and the corresponding temperature ranges (150-570 K) are determined. A high ionic conductivity in these solid solutions (~10−3-10−2 S/cm in the temperature range from 475 K to 550 K) is established, this fact not excluding the possibilities to use them for the production of materials with high ion conductive properties.

Ionic mobility and phase transition in heptafluorodiantimonate(III) Cs0.4Rb0.6Sb2F7

The ionic mobility and conductivity in the crystalline phase of Cs0.4Rb0.6Sb2F7 (I) is studied using 19F NMR, DSC, and impedance spectroscopy methods. The analysis of the 19F NMR spectra makes it possible to follow the character of ion motions in the fluoride sublattice in the temperature range of 150-470 K, and to determine the types and temperature ranges of these motions. It is found that diffusion of fluorine ions becomes the dominant type of ion motions in the modification formed as a result of the reversible phase transition (T = 415 K, the DSC data) in compound I. According to the preliminary results of electrophysical studies, the ionic conductivity in this compound is ~10−3 S/cm at temperatures above 450 K.