I. A. Sokolov

Electrical properties and the structure of halogen-containing lead borate glasses: I. The PbF2-2PbO.B2O3 system

The temperature and concentration dependences of the dc electrical conductivity of glasses in the PbF2–PbO · B2O3 system are investigated. It is found that the dependences logσ = f([PbF2]) and Eσ = f([PbF2]) for glasses containing ∼20 and ∼35 mol % PbF2 exhibit kinks, which are interpreted from the standpoint of the microinhomogeneous structure associated with the selective interaction of the components during the synthesis of glasses. Analysis of the transport numbers has revealed that the unipolar fluorine ionic conductivity is observed upon introduction of more than 35 mol % PbF2. It is shown that, in the concentration range from 0 to 35 mol % PbF2, the electric current is provided by both protons and fluorine ions.

Structure and electrical conductivity of glasses in the Na2O-Na2SO4-P2O5 system

The temperature-concentration dependence of the electrical conductivity of glasses in the Na2SO4-NaPO3 and Na2O-P2O5 systems has been investigated. Based on the obtained experimental data (IR spectra, density, microhardness, sound velocity, and paper chromatography), it has been demonstrated that SO42− ions form terminal groups through the incorporation into polyphosphate fragments of the structure of glasses in the Na2SO4-NaPO3 system. An increase in the electrical conductivity of glasses in this system by a factor of ∼1000 (as compared to NaPO3) at 25°C and a decrease in the activation energy for electrical conduction from 1.40 to 1.10 eV have been interpreted from the viewpoint of the decrease in the dissociation energy Ed of polar sulfate phosphate structural chemical fragments formed in the glass bulk upon introduction into sodium metaphosphate Na2SO4. This leads to an increase in the number of dissociated sodium ions, which are charge carriers, and to a decrease in the energy (Ea) of their activation shift in the sublattice formed by sulfate phosphate fragments of the structure.

Structure and electrical conductivity of Li2O-B2O3 glasses

The temperature-concentration dependence of the electrical conductivity of Li2O-B2O3 glasses in the temperature range of ∼180–310°C has been studied. For pure boron anhydride, the dependence logσ = f([1/T]) is linear, whereas for glasses with ∼2 mol % ≤ [Li2O] < ∼10 mol %, similar curves are kinked. At higher Li2O concentration the kinks disappear. Occurrence of kinks is attributed to variation of essence of current carriers from proton pattern for B2O3 to mixed proton-ion pattern for low-alkali glasses. Conductivity of glasses at [Li2O] ≥ 20 mol % is stipulated by the formation of a continuous sublattice of polar structuralchemical entities (entities) [BO4/2]−Li+ and the migration of lithium ions.

A Study of Ionic Conductivity of Glasses in the PbCl2–PbO · B2O3 and PbCl2–2PbO · B2O3 Systems

The steady-state electrical conductivity of oxychloride glasses in the PbCl2–PbO · B2O3 and PbCl2–2PbO · B2O3 systems is investigated. In the temperature range from ∼190 to ∼380°C, the dependence of logσ on the reciprocal of the temperature exhibits a linear behavior. The nature of charge carriers is studied using the Hittorf technique. It is demonstrated that protons and chlorine ions are charge carriers in solid glasses. The concentration dependence of the transport numbers of chlorine ions is examined by the Tubandt method. The contribution of the electronic component to the total electrical conductivity is estimated with the use of the Liang–Wagner technique. The concentration dependences of the electrical conductivity and the transport numbers of chlorine ions are interpreted in terms of the microinhomogeneous glass structure associated with the selective interaction of components during synthesis of glasses.

Proton conductivity of borate glass of the Me2O-B2O3 (Me = Na, Ag, Tl) system

The temperature-concentration dependences of glass conductivity in the Na2O-B2O3, Ag2O-B2O3, and Tl2O-B2O3 systems are studied. The nature of charge carriers in glass of these systems is revealed experimentally and their dependence on the concentration is studied. Based on the methods of Hittorf, Tubandt, Hebb-Liang-Wagner, and also on the fulfillment of Faraday’s Laws, it is shown that in glass of the Na2O-B2O3 system with [Na2O] < 15 mol %, the protons take part in the transport of charge in addition to sodium ions. The unipolar sodium conduction is attained at [Na2O] > 17 mol %. In glass of the Ag2O-B2O3 system, the conduction is associated with the migration of both silver ions and protons. For Ag2O concentrations from 15 to 22.5 mol %, the transport numbers of silver ions vary in a range from 0.45 to 0.53 and are virtually independent of the Ag2O content. In glass of the Tl2O-B2O3 system, the charge transfer is performed exclusively by protons. The contribution of the electronic component into the conductivity of glass in the systems studied does not exceed 0.01%. An interpretation of the temperature-concentration dependences of conductivity is put forward.

Structure and electric properties of Na2SO4-NaPO3 glasses

The influence of the SO42− ion on the temperature and concentration dependences of electric conductivity and the structure of sodium phosphate oxide glasses was studied. The increased electric conductivity of sulfate-phosphate glasses was explained by the formation of mixed sulfate-phosphate fragments with terminal SO42− ions in the structure of glasses in the Na2SO4-NaPO3 system. The dissociation energies of the sodium sulfate fragments are lower than those of pure oxide sodium phosphate structural units. As a result, the number of dissociated sodium ions increases, the activation energy of electric conductivity falls, and the conductivity (at 25°C) increases approximately 270-fold relative to the conductivity of NaPO3. The arrangement of SO42− ions in the structure was evaluated from the IR spectra of the glasses.

Electrical conductivity and the nature of charge carriers in glasses of the Tl2O-B2O3 system

The concentration dependence of the electrical conductivity of glasses in the Tl2O-B2O3 system is studied. The nature of charge carriers in this system is experimentally investigated for the first time. It is demonstrated using the Hittorf, Tubandt, and Hebb-Liang-Wagner techniques and the Faraday law that neither Tl+ ions nor electrons are involved in the electricity transport. The verification of the Faraday law does not reveal the presence of thallium in the amalgam of the cathode or a change in the sample weight after electrolysis, to within the experimental error. This allows one to make the inference that protons can be charge carriers in glasses of the Tl2O-B2O3 system. It is shown using extended X-ray absorption fine structure (EXAFS) spectroscopy that Tl3+ ions and thallium Tl0 reduced to the metallic state are absent in the structure of the glasses under investigation. This means that thallium in glasses of the Tl2O-B2O3 system occurs only in the form of Tl+ ions. The analysis of the IR spectroscopic data leads to only a qualitative conclusion that the water content in the glasses insignificantly increases with an increase in the thallium oxide content. An increase in the electrical conductivity of glasses in the Tl2O-B2O3 system with an increase in the thallium oxide content is explained by the increase in the number of protons formed upon dissociation of H+[BO4/2]− structural-chemical units, because their concentration increases with increasing Tl2O content. In the structure of boron oxide, impurity hydrogen enters predominantly into the composition of H+[O2/2BO−] structural-chemical units, for which the dissociation energy is higher than that for the H+[BO4/2]− structural-chemical units. The increase in the concentration of H+[BO4/2]− structural-chemical units is accompanied by the increase in the number of dissociated protons, which are charge carriers in glasses of the Tl2O-B2O3 system.

The nature of charge carriers and their transport numbers in glasses of the Ag2O-B2O3 system

The temperature-concentration dependence of the dc electrical conductivity of glasses in the xAg2O-(1 − x)B2O3 (0.05 ≤ x ≤ 0.25) system is investigated using active (amalgam) electrodes. A series of glasses are synthesized with the use of D2O as an isotope tracer. The analysis of data on the electrolysis of glasses at 0.15 ≤ x ≤ 0.225 demonstrates that charge carriers in these glasses involve protons formed upon dissociation of impurity water. The water content is evaluated by IR spectroscopy. The electronic component of the total electrical conductivity is determined by the Liang-Wagner technique. It is shown that the contribution of the electronic component does not exceed the sensitivity of the technique (10−2—10−3%). The participation of silver ions in electricity transport processes is studied by the Hittorf method. It is demonstrated that their transport numbers do not exceed 0.53. A comparison of the physicochemical properties of glasses in the Ag2O-B2O3 and Na2O-B2O3 systems shows that sodium and silver ions occupy different positions in the structure.

Structure of lithium-niobium phosphate glass promising for optical phase elements creation with femtosecond laser radiation

Spectral studies are carried out and crystallization processes of niobium-containing phosphate glass with a high content of lithium oxide are studied for further research of the structural transformations in them caused by exposure to femtosecond laser radiation.

Development of the R.L. Muller model of the microheterogeneous structure of glass and its application for various glass types

The possibility of the application of the R.L. Muller model of the microheterogeneous structure of glass for the description of the nature of the conduction various glass classes, the electric conduction of which is due to the migration of cations, anions and the combined migration of cations and electrons, has been considered. It was shown that the appearance and the subsequent increase in the ionic conduction can be explained using the concentration variation of the blocking extent function (γ), which is calculated based on the analysis of the ratio of the concentration of nonpolar and polar structural fragments—structural-chemical units in the bulk of glass. On the whole, the methodology of the calculation of the concentration γ values for various glass systems coincides, except for some features in halogen-containing systems that required additional specifications.