N. N. Savchenko

Internal mobility, phase transitions, and ionic conductivity in (NH4)6KZr4F23 and (NH4)6KHf4F23

The ion mobility, phase transitions (PTs), and conductivity in (NH4)6KZr4F23 (I) and (NH4)6KHf4F23 (II) have been studied by 1H and 19F NMR, DSC, and impedance spectroscopy. Types of ion motion in the fluorides and ammonium sublattices have been determined in the temperature range 150–480 K, and their activation energies have been evaluated. Compounds I and II undergo phase transitions in the temperature ranges 400–440 and 419–440 K, respectively, to form high-temperature modifications. The high ionic conductivity in (NH4)6KZr4F23 and (NH4)6KHf4F23 (>10−3 S/cm at 473 K) makes it possible to classify these compounds with superionic conductors.

(NH4)4M(Zr(Hf))3F17 · 2HF Complexes (M = Li, Na): Synthesis and Physicochemical Properties

Monoclinic crystals of ammonium hydrofluoride fluoro complexes of zirconium and hafnium (NH4)4M(Zr(Hf))3F17 · 2HF (M = Li, Na) are synthesized and studied. Their unit cell parameters are determined. IR spectra of the synthesized compounds are measured in the range of 350–4000 cm–1.

Ionic conduction in glasses in the MnNbOF5-BaF2-BiF3 system

The electrical conductivity of oxyfluoride glasses in the MnNbOF5-BaF2-BiF3 system in the temperature range 299–550 K was studied by impedance spectroscopy. It was shown that the conductivity is mainly caused by fluoride ions forming fluorobismuth polyhedra in the glass structure, being as high as 7.46 × 10−3 S/cm (533 K) in the 20MnNbOF5-30BaF2-50BiF3 system reaches, which is at the level of the best values for fluoride glasses.

Synthesis and characterization of bismuth-containing oxyfluoroniobate glasses

New glasses are prepared in the MnNbOF5-BaF2-BiF3 system. The thermal parameters of these glasses are analyzed as influenced by bismuth trifluoride. IR and Raman spectroscopy shows that the glass structures are built of Nb(O, F)6 polyhedra, which are linked by oxygen bridges to form glass nets via. A medium-order order region in the glass includes fluoroniobate polyhedra not linked directly to bismuth trifluoride polyhedra. A Ba0.55Bi0.45F2.45 crystalline phase is discovered at 320°C in a glass of composition 20MnNbOF5-40BaF2-40BiF3.

New zirconium fluoride complexes (NH4)6MZr4F23 (M = K, Rb, and Cs): Synthesis and physicochemical properties

Ammonium-containing zirconium fluoride complexes of the formula (NH4)6MZr4F23 (M = K, Rb, and Cs) were obtained and studied. The complexes crystallize in the orthorhombic system. Their unit cell parameters were determined. The IR absorption spectra of the complexes in the 350–4000 cm−1 range were recorded and examined.

Phase transitions, ion mobility, and conductivity in fluoro complexes (NH4)6RbZr4F23 and (NH4)6RbHf4F23

Ion mobility, phase transitions (PT), and conductivity in compounds (NH4)6RbZr4F23 (I) and (NH4)6RbHf4F23 (II) were studied by 1H and 19F NMR spectroscopy, X-ray powder diffraction (XRD), DSC, and impedance spectroscopy. Ion movement modes in fluoride and ammonium sublattices of both compounds were determined in temperature range 150–480 K and their activation energy was assessed. Phase transitions in compounds I and II were revealed in temperature ranges 400–440 and 419–440 K resulting in formation of α modifications where diffusion of fluoride and ammonium ions becomes the dominant kind of ion movement. High ionic conductivity in fluoride II (σ ~ 7.7 × 10–3 S/cm at 463 K) indicates that this compound belongs to the class of superionic conductors.

Synthesis and physicochemical properties of new hafnium fluoro complexes (NH4)6MHf4F23 (M = K, Rb, Cs)

Ammonium-containing hafnium fluoro complexes (NH4)6MHf4F23 (M = K, Rb, Cs), which crystallize in orthorhombic symmetry, were synthesized and studied. Their unit cell parameters were determined. The IR absorption spectra of the synthesized complexes were studied in the region of 350–4000 cm−1.

Glass Formation in Niobium Fluoride Systems

Various variants of producing niobium fluoride glasses using niobium pentafluoride and its oxyfluoride compounds as precursors were studied.

InF3-based bismuth-containing glasses

Glasses have been prepared in the InF3-BiF3-BaF2-PbF2-ZnF2-LnF3 (Ln = Eu, Tm) system. The short-range and medium-range order structure of the glass network is discussed on the basis of IR and Raman spectroscopy data. The effect of bismuth trifluoride on the thermal properties, structure, and photo-luminescence properties of glasses was studied. Bismuth trifluoride doping improves the thermal parameters of glasses. The polyhedra formed by bismuth trifluoride in the glass are not involved in the medium-range order. In rare-earth-containing glasses, strong photoluminescence was discovered in the range 530–560 nm with excitation by the Raman-masking 532-nm wavelength. Bismuth in the glass enhances the europium photoluminescence level in the glass of the InF3-BiF3-BaF2-PbF2-ZnF2-EuF3 system.

Structure and properties of core-shell microparticles in paraffin-ultradispersed polytetrafluoroethylene systems

Microsized spherical core-shell particles consisting of hydrocarbon cores encapsulated into fluoropolymer shells are obtained in supercritical carbon dioxide. Paraffins serve as a core material, while the polymer shell is formed from ultradispersed polytetrafluoroethylene. The morphology and molecular structure in the bulk and on the surface of the particles and the influence of conditions of particle formation on the shell thickness and the thermal properties of the materials are studied. The materials are composites comprised of paraffin cores coated with shells of loosened globular fluoropolymer particles with sizes of 0.2–1.7 μm. The shells is built of low- and high-molecular-mass fractions consisting of CF3(CF2)nCF3 molecular chains with different lengths. The shell thickness is governed by preparation conditions, exposure time, and the percentage of the polymer in the initial dispersion.