V. K. Goncharuk

Ion mobility and transport in β-PbF2 doped with alkaline-earth fluorides

We have studied ion mobility and conduction in (1 − x)PbF2 · xMF2 (M = Mg2+, Ca2+, Sr2+, Ba2+; 0.05≤x≤0.1) solid solutions by 19F and 207Pb NMR and impedance spectroscopy. The results are used to analyze the factors governing the structure of the fluoride sublattice and the nature and energetics of ionic motion in the temperature range 170–550 K. The solid solutions are shown to have high ionic conductivity (∼10−4 to 10−3 S/cm at temperatures above 470 K, with activation energies Ea ≤ 0.3−0.6 eV) and are, therefore, potentially attractive for engineering materials with tailored electrical properties.

Ionic mobility and electrical transport in 45ZrF4 · 35BiF3 · 20MF (M - Li, Na, K) glasses studied by NMR and impedance spectroscopy

The ionic mobility and electrical transport in 45ZrF4 · 35BiF3 · 20MF (M - Li, Na, K) glasses have been studied by 7Li, 19F, and 23Na NMR and impedance spectroscopy at temperatures from 200 to 500 K. In the range 400–440 K, the main kinds of ionic mobility in these glasses are local motions of fluorine-containing groups and lithium ion diffusion. The temperature range where the dominant kind of ion motion in the glasses is fluoride ion diffusion depends on the nature of the M+ cation. Above 470 K, the glasses offer rather high ionic conductivity: σ ≥ 10−5 S/cm.

Glass formation in the ZrF4-BiF3-MeF (Me = Li, Na, K) fluoride systems

The glass formation in the ZrF4-BiF3-MeF (Me = Li, Na, K) systems is investigated. Bismuth fluorozirconate glasses are synthesized in this system, and their thermal and optical properties are described.

Ionic mobility and conduction in the 50PbF2 · 30BiF3 · 20NaF solid solution studied by NMR and impedance spectroscopy

Ionic mobility and electrical transport in the 50PbF2 · 30BiF3 · 20NaF fluorite solid solution have been studied by 19F and 23Na NMR and impedance spectroscopy. Analysis of the NMR spectra allowed us to assess the temperature effect on the nature of ion motion in the fluorine and sodium sublattices, to identify the types of ionic mobility, and determine the corresponding temperature ranges. The results demonstrate that, at temperatures above 390 K, the dominant type of ion motion in 50PbF2 · 30BiF3 · 20NaF is the diffusion of fluoride and sodium ions. The ionic conductivity of the solid solution reaches 4.4 × 10−4 S/cm at 535 K, suggesting that the 50PbF2 · 30BiF3 · 20NaF solid solution can be used as a key component for engineering new functional materials.

Medium-range order and physicochemical properties of (100 − x)(0.5PbO · 0.5P2O5) · xTeO2 glasses in terms of the constant stoichiometry grouping concept

Glasses in the (100 − x)(0.5PbO · 0.5P2O5) · xTeO2 section of the PbO-P2O5-TeO2 system have been synthesized over the entire composition range for the first time and their properties (Raman spectra, refractive index n, density d, glass transition temperature Tg, and light scattering losses) have been investigated. It has been demonstrated that the Raman spectra can be represented as a superposition of constant spectral forms corresponding to constant stoichiometry groupings PbO · P2O5, TeO2 · 2PbO · 2P2O5, TeO2 · PbO · P2O5, 2TeO2 · PbO · P2O5, and TeO2. The existence of crystals of the corresponding stoichiometry has been predicted using the constant stoichiometry grouping concept. The diagram of the constant stoichiometry grouping contents (determined from the Raman spectra) in glasses of the system under investigation has made it possible to determine the partial properties of constant stoichiometry groupings, to calculate the dependences of the refractive index and density on the composition, and to refine the values of n and d for vitreous tellurium dioxide and lead metaphosphate. The practical importance of glasses in the system under consideration for the use in photonic devices has been discussed.

Ionic mobility, ionic transport, and charge transfer mechanism in solid solutions (1 − x)PbF2-xMF n by the NMR and impedance spectroscopy data

The internal mobility and ionic conduction of solid solutions in systems PbF2-MF2 and PbF2-MF3 are studied by the NMR (19F, 27Al, 207Pb) and impedance spectroscopy methods. Factors that define the form of ionic movements and their energy characteristics in the temperature region 150 to 550 K are considered and analyzed. Temperature shifts of the frequency range that defines the ionic conduction of solid solutions are discovered on the basis of impedance spectroscopy data and explained. It is established that the high ionic conductance in lead difluoride doped with fluorides of metals of Groups II and III is caused by the diffusion of fluoride ions. The large values of specific conductance (10−4 to 10−3 S cm−1) at a relatively low activation energy (less than 0.6 eV) allow one to consider the solid solutions studied in the role of a basis for the obtaining of new fluoride materials with high ionic conductance.

Mobility of Fluorine Ions and Electrical Conductivity in InF3–BaF2–BiF3Glasses

The dynamics of the fluorine subsystem in InF3–BaF2–BiF3glasses was characterized by 19F NMR spectroscopy, impedance spectroscopy, and electrical conductivity measurements. The results demonstrate that increasing the BiF3content improves the dynamic characteristics of the fluorine subsystem and increases the conductivity of the glasses.

Ionic Mobility in Glasses in the ZrF4-BiF3-MF Systems (M = Li, Na, K) as Probed by 7Li, 19F, and 23Na NMR

The ion mobility in new fluoride glasses (mol %) 45ZrF4 · 25BiF3 · 30MF (I) (M = Li, Na, K), (70 - x)ZrF4 · xBiF3 · 30LiF (II) (15 ≤ x ≤ 35), and 45ZrF4 · (55-x)BiF3 · xMF (III) (M = Li, Na; 10 ≤ x ≤ 30) has been studied by 7Li, 19F, and 23Na NMR in the temperature range 250–500 K. The character of ion motion in bismuth fluorozirconate glasses I and III is determined by temperature and the nature and concentration of an alkali-metal cation. Major type of ion mobility in glasses I–III at temperature 400–440 K are local motions of fluorine-containing moieties and diffusion of lithium ions (except for the glass with x = 10). The factors responsible for diffusion in the fluoride sublattice of glasses I have been determined. Sodium ions in glasses I and III are not involved in ion transport.

Composite materials based on fluoropolymers and oxyfluoride glasses

It was shown that molded specimens of polymer composite materials can be obtained by an extrusion method by melt blending of Fluoroplast F-2 MB (modified poly(vinylidene difluoride)) and oxyfluoride glasses of the composition 3B2O3 (40SnF2–30SnO–30P2O5). The compositions of the observed phases of the composites were determined. Conclusions were made on the incompatibility of the components, their dispersion distribution, and strong adhesion interaction. Data on the nano level of the blending of the components were obtained. The elongation and Brinell hardness were measured in the composites with various (0–50 vol %) oxyfluoride contents. It was concluded that it is possible to produce composites based on fluorinated hydrocarbon and fluoroxide polymers.

Glass formation in the fluoride system ZrF4-BiF3-BaF2

The glass formation in the system ZrF4-BiF3-BaF2 has been investigated in the composition range (75–30)ZrF4-(0–60)BiF3-(0–40)BaF2, mol %. The synthesis and thermal and optical properties of bismuth-barium-fluorozirconate glass were described. As was shown by the DSC (differential scanning calorimetry) method, at the BiF3 content of 20–35 mol %, glass with the highest stability against crystallization was formed. Further stabilization of the vitreous state can be attained using additives of alkali metals and trifluorides.