Structure and electrical conductivity of glasses in the Na<Subscript>2</Subscript>O-Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> 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 E _d 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 (E _a) of their activation shift in the sublattice formed by sulfate phosphate fragments of the structure.     

Glass formation and electrical conductivity of glasses in the Na<Subscript>2</Subscript>Se-P<Subscript>2</Subscript>Se<Subscript>5</Subscript> system in a wide temperature range

The glass formation region in the Na₂Se-P₂Se₅ system and the temperature-concentration dependences of the electrical conductivity of glasses have been investigated over a wide range of temperatures. The densities and glass transition temperatures T _g of glasses have been determined. A comparison of the electrical conductivity of glasses in the Na₂Se-P₂Se₅ and Na₂O-P₂O₅ systems has demonstrated that the conductivity of selenium-containing glasses (at 25°C) is approximately three orders of magnitude higher than the electrical conductivity of oxide glasses. The assumption has been made that an increase in the electrical conductivity of glasses with selenium is caused by the increase in the degree of dissociation of Na⁺[Se⁻PSe_3/2] polar structural chemical units and the higher mobility of sodium ions in the oxygen-free matrix.     

Electrical conductivity and the nature of charge carriers in glasses of the Tl<Subscript>2</Subscript>O-B<Subscript>2</Subscript>O<Subscript>3</Subscript> 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⁺[BO_4/2]^? 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⁺[O_2/2BO^?] structural-chemical units, for which the dissociation energy is higher than that for the H⁺[BO_4/2]^? structural-chemical units. The increase in the concentration of H⁺[BO_4/2]^? 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.     

Migration processes in the glass forming melts of the Na<Subscript>2</Subscript>O–BaO–Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> system

The specific conductivity and tracer of diffusion of sodium and barium ions have been determined and the values of the transport numbers and correlation factor for diffusion have been calculated in two melts of the Na₂O–BaO–Ga₂O₃–SiO₂ system.     

<Superscript>22</Superscript>Na diffusion and electrical conductivity of alkali-free silicate glasses

The diffusion of sodium ions in silica glasses produced by different methods and glasses in the Al₂O₃-R₂O₃-SiO₂ (R = La, Pr, Nd, Sm, Tb) systems has been investigated by the radioactive tracer method. The diffusion mobility of ²²Na ions in the aluminosilicate glasses containing rare-earth element oxides is close to that in the KSG silica glass prepared by high-temperature hydrolysis of silicon tetrachloride SiCl₄. A comparison of the diffusion coefficients with the electrical conductivity of the glasses has demonstrated that the conduction in the KI silica glass is due to the migration of sodium ions. In the KSG glass, as well as in the aluminosilicate glasses containing rare-earth element oxides, sodium ions are not charge carriers.     

Kinetics of crystal nucleation of Na<Subscript>2</Subscript>O · 2CaO · 3SiO<Subscript>2</Subscript>-based solid solutions in glasses of the Na<Subscript>2</Subscript>SiO<Subscript>3</Subscript>—CaSiO<Subscript>3</Subscript> pseudobinary join

The kinetics of crystal nucleation is investigated in sodium calcium silicate glasses of two compositions (22.4 and 24.4 mol % Na₂O), which belong to the Na₂SiO₃—CaSiO₃ pseudobinary join and, according to the phase diagram, lie in the region of the formation of solid solutions between the compositions Na₂O · 2CaO · 3SiO₂ and Na₂O · CaO · 2SiO₂. The stationary rate of crystal nucleation of Na₂O · 2CaO · 3SiO₂-based solid solutions is measured as a function of temperature. It is shown that the maximum stationary rate of nucleation increases with an increase in the sodium oxide content in the initial glasses. The experimental data are analyzed in the framework of the classical nucleation theory.Original Russian Text Copyright © 2004 by Fizika i Khimiya Stekla, Soboleva, Yuritsyn, Ugolkov.     

Effect of the relative volume of the conducting phase on the electroconductivity of glasses in the Na<Subscript>2</Subscript>O–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> system

The effect of the relative volume of the conducting phase on the electroconductivity of phase-separated glasses in the ternary system Na₂O–B₂O₃–SiO₂, whose compositions are on the same glass transition isotherm at 550°C, is investigated. It is demonstrated that the electroconductivity of phase-separated sodium borosilicate glasses does not depend on the relative volume of the conducting phase (within the limits from 0.3 to 0.9) under the condition that its composition invariable.     

Calculations of the Thermodynamic Properties of Glasses and Melts in the Na<Subscript>2</Subscript>O-SiO<Subscript>2</Subscript> and B<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> Systems on the Basis of the Generalized Lattice Theory of Associated Solutions

The possibility of calculating the thermodynamic properties of binary glass-forming systems containing both modifier (Na₂O) and glass-former (B₂O₃) oxides with the use of the vacancy variant of the generalized lattice theory of associated solutions is demonstrated for glasses and melts in the Na₂O-SiO₂ and B₂O₃-SiO₂ systems.     

Electrical conductivity of CuI-AsI<Subscript>3</Subscript>-As<Subscript>2</Subscript>Se<Subscript>3</Subscript> and CuI-SbI<Subscript>3</Subscript>-As<Subscript>2</Subscript>Se<Subscript>3</Subscript> chalcogenide films prepared by chemical deposition

The electrical conductivity of chalcogenide semiconductor films in the CuI-AsI₃-As₂Se₃ and CuI-SbI₃-As₂Se₃ systems, which have been prepared by chemical deposition from mono-n-butylamine, has been studied as a function of the temperature and film composition. It has been established that the electrical conductivity of the CuI-AsI₃-As₂Se₃ and CuI-SbI₃-As₂Se₃ films is predominantly determined by the copper iodide content. It has been demonstrated that the electrical properties of the chalcogenide glasses and the related films are characterized by the same values to within the experimental error, which is explained by the same model of dissolution of vitreous semiconductors in amines with the retention of the electrical properties of chalcogenide glasses after the deposition of films from their solutions.     

On the structure of glasses in the BaO-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> system

The structure of single-phase glasses in the BaO-B₂O₃-SiO₂ system has been studied by the large- and small-angle X-ray scattering techniques. The glasses containing 40 mol % BaO upon equimolar replacement of B₂O₃ by SiO₂ have been investigated. It has been demonstrated that the incorporation of barium ions into structural groupings fixes their position and provides ordering in the distribution of barium ions at interatomic distances up to at least 5 Å. The glasses under investigation are homogeneous, and their inhomogeneity is determined by thermal density fluctuations and fluctuations of the concentration of a part of barium ions distributed in a statistically random manner in the volume of the glass. The observed ordering in the distribution of barium ions is not reduced to the formation of local clusters with an increased concentration of barium ions but is most likely a characteristic feature of the bulk glass structure. The glass structure is consistent with the model of ideal associated solutions.     

Mechanism of formation of the complex oxide Na<Subscript>2</Subscript>Nd<Subscript>2</Subscript>Ti<Subscript>3</Subscript>O<Subscript>10</Subscript>

The processes of phase formation in the Nd₂O₃-TiO₂-Na₂CO₃ system have been investigated in the temperature range 500–1100°C. The mechanism of the high-temperature solid-phase reaction of formation of the complex oxide Na₂Nd₂Ti₃O₁₀ has been studied. It has been established that the Na₂Nd₂Ti₃O₁₀ compound is formed from the intermediate product Na_0.5Nd_0.5TiO₃ with a perovskite structure in the temperature range 830–890°C and from the NaNdTiO₄ oxide with a perovskite-like layered structure in the temperature range 960–1100°C.     

On the Nature of Current Carriers in Glasses of the NaF–Na2O–B2O3 System

Glasses in the Na₂O–B₂O₃, NaF–Na₂O–B₂O₃, and NaF–B₂O₃ systems have been synthesized. The nature of current carriers and their transport numbers in these glasses are determined by the Hittorf and Tubandt techniques. The concentration dependences of the electrical conductivity and the transport numbers are investigated. It is demonstrated that the electricity transport in glasses in the NaF–B₂O₃ system is provided by sodium and fluorine ions. The results obtained are interpreted in terms of the microinhomogeneous glass structure.     

Synthesis and Spectral Properties of Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>-Doped Sodium Silicophosphate Glass

Combined UV-visible and FTIR spectral studies of undoped and Nd₂O₃ –doped sodium silicophosphate glasses were carried out to characterize the optical and structural properties of such glasses. The base undoped silicophosphate glass exhibits strong UV absorption which is due to the presence of unavoidable trace iron impurities (mainly Fe³⁺ ions) present contaminated within the raw materials used for the preparation of such glasses. Nd₂O₃ –doped glasses show characteristic absorption bands extending in the entire visible region which are attributed to the contribution of Nd³⁺ ions with distinct peaks which are almost constant with the increase of dopant. This comes from the combined compact glass structure containing two glass forming units and the shielding of the rare-earth ions. Infrared absorption spectra of the studied glasses reveal characteristic IR bands due to the combination of both silicate and phosphate groups. The introduction of Nd₂O₃ within the dopant level (2 %) produces no variations in the IR vibrational bands due to the presence of the two structural silicate and phosphate groups giving compactness of the network structure. The deconvoluted spectra reveal the presence of phosphate groups in a slightly high ratio due to the high content of P₂O₅ in the composition.     

Electrical conductivity of CuI-Cu<Subscript>2</Subscript>Se-As<Subscript>2</Subscript>Se<Subscript>3</Subscript> chalcogenide films prepared by chemical deposition

The electrical conductivity of CuI-Cu₂Se-As₂Se₃ chalcogenide semiconductor films prepared through the chemical deposition from an organic solvent has been investigated as a function of the temperature and composition of the films. It has been established that the electrical properties of the chalcogenide glasses and related films are characterized by the same values within the limits of the experimental error. This result is in agreement with the model of dissolution of vitreous semiconductors in organic bases (amines), according to which the main properties of bulk (cast) chalcogenide glasses are retained in films prepared from these glasses.     

Europium(II) in glasses of the Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript>-MnO-Eu<Subscript>2</Subscript>O<Subscript>3</Subscript> system

Triply and doubly charged states of europium are revealed by ¹⁵¹Eu Mössbauer spectroscopy in the structure of glasses of the composition (mol %) 19.5Al₂O₃, 31.5SiO₂, 26.5MnO, and 22.5Eu₂O₃. The isomer shifts in the Mössbauer spectra of Eu³⁺ and Eu²⁺ ions in the structure of glasses differ from the isomer shifts in the spectra of the Eu₂O₃ and EuO compounds. This difference is explained by the fact that the electron density at ¹⁵¹Eu nuclei is affected by the manganese and aluminum atoms, which are not bound directly to the europium atoms. The broadening of the spectra of the Eu²⁺ ions in glasses is caused by the nonuniform isomer shift.     

Spectroscopic Inquiry of the Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-role in Binary Sodium Borate,Sodium Silicate and Sodium Phosphate Glasses and Effects of Gamma Irradiation

Optical absorption spectral investigations have been carried out on Fe³⁺ ions doped sodium borate, sodium silicate and sodium phosphate glasses before and after gamma irradiation. The UV-visible absorption spectrum exhibits bands characteristic of Fe³⁺ ions coordination in each system. Interesting aspects of FT-IR spectra were found, and this gives information about the structure changes in the constituent units of these glass systems as a function of Fe₂O₃ concentration. All glasses reveal characteristic absorption bands due to the addition of different ratios of iron which explain the state of iron in each system in terms of its valence and coordination number. Results indicate that iron favors a higher oxidation state (tetrahedral coordination) in the case of sodium silicate glasses. The doping with progressive Fe₂O₃ additions (0.5?7.5 %) has some effect on the number and position of the characteristic bands due to formation of FeO₄ groups. The IR absorption spectra after irradiation reveal limited changes in the intensity which can be correlated with minor changes in bond angles and /or bond lengths within the structural units by irradiation.     

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.     

On the fluctuation structure of single-phase glasses in the SrO-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> system

The structure of single-phase glasses in the SrO-B₂O₃-SiO₂ system has been studied by the small-and large-angle X-ray scattering technique. The glasses containing 35, 40, and 45 mol % SrO upon equimolar replacement of B₂O₃ by SiO₂ have been investigated. It has been demonstrated that the glasses do not contain chemical inhomogeneity regions. The inhomogeneity of the glasses is determined only by thermal density fluctuations. The isothermal compressibility varies insignificantly upon replacement of B₂O₃ by SiO₂ and decreases with an increase in the SrO content. The glass structure is consistent with the model of ideal associated solutions.     

Optimization of High Conducting Na<Subscript>3</Subscript>Zr<Subscript>2</Subscript>Si<Subscript>2</Subscript>PO<Subscript>12</Subscript> Phase by new Phosphate Salt for Solid Electrolyte

A composition of NASICON (Na₃Zr₂Si₂PO₁₂) was synthesized by the solid-state reaction method using a new compound Na₂HPO₄2H₂O. The X-ray diffraction patterns of all samples exhibit monoclinic Na₃Zr₂Si₂PO₁₂ as a major phase with a very small amount of monoclinic-ZrO₂. The maximum relative density (97 %) and maximum conductivity is obtained in the samples sintered at 1200 °C (N3) which is slightly higher than β-Al₂O₃. The activation energy is ～ 0.20 eV for the N3 sample which is lower than for β-Al₂O₃. The dilatometeric study and Arrhenius plots confirmed a phase transition of NASICON from monoclinic to rhombohedral. The micro-structural study of the samples done by scanning electron microscopy (SEM) indicated a significant influence of the processing conditions on the microstructures. Raman spectroscopy demonstrated that the sample N3 exhibits minor structural changes compared to other samples.     

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 log 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.