Concentration dependence of electric conductivity for fluorine-containing sodium borate glasses

The influence of sodium fluoride additives on the physicochemical properties of glasses in the Na₂O-B₂O₃ systems is investigated. The introduction of sodium fluoride into the Na₂O · 2B₂O₃ and Na₂O · 3B₂O₃ glasses leads to an increase in the electric conductivity. The temperature-concentration dependence of the electric conductivity has been investigated. It is shown that, in glasses of the NaF-Na₂O · 2B₂O₃ system, an increase in the volume concentration of sodium ions from 2.4 × 10⁻² to ∼3 × 10⁻² mol/cm³ is accompanied by an insignificant decrease in the activation energy E_σ from 1.44 to 1.38 eV and a sharp (by a factor of ∼30) increase in the electric conductivity. In glasses of the NaF-Na₂O · 3B₂O₃ system, an increase in the concentration of sodium ions from 1.8 × 10⁻² to ∼2.3 × 10⁻² mol/cm³ brings about an increase in the electric conductivity by a factor of approximately 100 and an increase in E_σ from 1.6 to 1.83 eV. A further increase in the concentration of sodium ions (up to 2.5 × 10⁻² mol/cm³) virtually does not affect the electric conductivity and E_σ. At the same concentration of sodium ions (∼2.46 × 10⁻² mol/cm³) in the 9.8NaF · 90.2[Na₂O · 2B₂O₃] and 57.1NaF · 42.9[Na₂O · 3B₂O₃] glasses, the electric conductivity and the activation energy are considerably higher in the glass with a larger fluorine content. The regularities revealed are interpreted in the framework of the microinhomogeneous glass structure.     

Enhancing the electrical conductivity of vanadate glass system (Fe2O3, B2O3, V2O5) via doping with sodium or strontium cations

Novel glass-ceramics of the nominal molar compositions 20Fe₂O₃·20B₂O₃·(60-x)V₂O₅· (xNa₂O or xSrO) (where x?=?0 or 10) were prepared by traditional melt technique. Differential thermal analysis (DTA) was implemented to study the thermal behavior of the prepared glasses. Vanadium pentoxide (V₂O₅), iron vanadate (FeVO₄), sodium vanadate (Na₃VO₄) and strontium vanadate (with different formulae) were crystallized and identified by X-ray diffraction (XRD) analysis under certain conditions of heat-treatment. Further characterization of glass and glass ceramics samples were performed using scanning electron microscope (SEM), density, electrical and dielectric measurements. In conclusion, our study elucidated that the substitution of vanadium by Na⁺ and Sr²⁺ ions enhanced the conductivity at 180?°C from 5.11?×?10^?4 for unmodified glass to 2.93?×?10^?3 and 1.03?×?10^?2?S?cm^?1 for Na- and Sr-modified glasses.     

Electrical conductivity and structure of glasses in the Na<Subscript>2</Subscript>O-Na<Subscript>2</Subscript>S-P<Subscript>2</Subscript>O<Subscript>5</Subscript> and Na<Subscript>2</Subscript>S-P<Subscript>2</Subscript>S<Subscript>5</Subscript> systems

The glasses, in which oxygen was partially replaced with sulfur, have been synthesized in the Na₂O-P₂O₅-Na₂S system. The chemical and chromatographic analyses of the glasses synthesized have been performed. The temperature-concentration dependences of electrical conductivity of the glasses have been studied over a wide temperature range; the glass transition temperatures and the nature of charge carriers have been determined. The IR spectra and Raman spectra have been recorded at room temperature; the density and microhardness of the glasses and ultrasound velocity have been measured. A comparison of the electrical conductivities of the investigated glasses with those of the earlier studied glasses in the Na₂O-P₂O₅ system has shown their fair coincidence. The introduction of sodium sulfide into the Na₂O-P₂O₅ system is accompanied by an approximately threefold increase in electrical conductivity, although the concentrations of charge carriers (sodium ions) in the glasses amount to ∼17 and ∼26 mmol/cm³, respectively. The rise in electrical conductivity has been assumed to be caused by the increase in the degree of dissociation of polar structural chemical units including sulfide ions and by the higher mobility of sodium ions in the oxygen-free matrix.     

Synthesis,crystal structure and dehydration kinetics of NaB(OH)<Subscript>4</Subscript>·2H<Subscript>2</Subscript>O

Sodium metaborate tetrahydrate (NaB(OH)₄·2H₂O) was synthesized by reaction of anhydrous borax (Na₂O·2B₂O₃) with sodium hydroxide (NaOH) under conditions at 90 °C for 150 min. The structure was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM) and Thermogravimetric (TG) analyses. Moreover, dehydration kinetics of NaB(OH)₄·2H₂O was carried out under non-isothermal conditions and the Coats-Redfern method was applied to analyze the TG data for calculation of activation energies (E _a ) and pre-exponential factors (k _o ) for different heating rates. It was determined that dehydration of sodium metaborate tetrahydrate occurred in five steps. According to the Coats-Redfern non-isothermal model, E _a and k _o were calculated as 50.89 kJ/mol and 26×10⁴ min⁻¹ for region I, 18.51 kJ/mol and 0.87×10³ min⁻¹ for region II, 15.72 kJ/mol and 0.52×10³ min⁻¹ for region III, 4.37 kJ/mol and 0.04×10³ min⁻¹ for region IV and 37.42 kJ/mol and 8.56×10³ min⁻¹ for region V, respectively.     

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.     

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.     

RELATION OF ELECTRICAL CONDUCTIVITY TO CHEMICAL COMPOSITION OF GLASS*

The electrical conductivity of some glasses in the soda-lime-silica system was measured at 400 °C. with an apparatus which is described. The specific resistance at this temperature ranged from 0.06 to 5.0 × 10⁵ ohms per cc. Measurements were made on other glasses containing equivalent amounts of various oxides incorporated in a parent soda-lime-silica glass. It was found that an increase in resistance was produced by additions of MnO, ZnO, B₂O₃, Fe₂O₃, BaO, PbO, TiO₂, and K₂O, the resistances increasing in this order. A decreased resistance was produced by Na₂O, CaO, and Al₂O₃. Previously published data on the power factors of these glasses are reviewed.     

Electrical Properties and the Structure of Glasses in the xNa2O–(1 – x)2PbO · B2O3 System

The temperature–concentration dependences of the electrical conductivity and the activation energy for electrical conduction of glasses in the Na₂O–B₂O₃ and Na₂O–2PbO · B₂O₃ systems are studied. The investigation into the nature of the electrical conduction in these glasses reveals that the contribution from the electronic component (10^–3%) of the conductivity is within the sensitivity of the Liang–Wagner technique. A considerable alkali conductivity is observed upon introduction of more than 12 mol % Na₂O. The true transport number of sodium _Na is as large as unity at [Na₂O] 15 mol %. It is shown that the observed temperature–concentration dependences of the electrical and transport properties are governed by the ratio between the concentrations of polar and nonpolar structural–chemical units of the Na⁺[BO_4/2]^–, Na⁺[O^–BO_2/2] Na⁺[O^–BO_2/2], Pb²⁺ _1/2[BO_4/2]^–, Pb²⁺ _1/2[O^–BO_2/2], and [BO_3/2] types.     

Influence of MeF2 (Me = Mg, Ca, Sr, and Ba) on the electrical properties of glasses in the MeF2-Na2B4O7 system

Glasses in the MeF₂-Na₂B₄O₇ (Me = Mg, Ca, Sr, and Ba) system have been synthesized. It is shown that the glass formation is observed at a MeF₂ content of up to 40 mol %. The influence of the MeF₂ content on the electrical conductivity and the fluorine concentration in the glass bulk is examined. From the analysis of the concentration dependence of the electrical conductivity with due regard for the fluorine content, it is concluded that the glass structure is predominantly built up of the polar groupings Na⁺[BO_4/2]^-, Na⁺[F-BO_3/2], Me _1/2 ²⁺ [BO_4/2]⁻, Me _1/2 ²⁺ [F⁻BO_3/2], [MeF_4/2], and [MeF_6/3] and the BO_3/2 nonpolar structural-chemical units. The electricity transport is governed by the migration of sodium ions formed upon dissociation of the Na+[BO_4/2]^-and Na+[F^-BO_3/2] groupings. An increase in the MeF₂ content leads to a decrease in the total concentration of sodium ions, a decrease in the Na⁺[BO_4/2]^- concentration, and an increase in the Na⁺[F^-BO_3/2] concentration. Upon introduction of MeF₂ up to ∼20 mol %, the fluorine losses during the synthesis are caused by the dehydration of glass melt. An addition of 20–25 mol % MeF₂ brings about the saturation of the glass by the [F^-BO_3/2]-type structural units, so that the fluorine concentration reaches a saturation in the structures of calcium-, strontium-, and barium-containing glasses and increases in magnesium-containing glasses, owing to the formation of the [MgF+_6/3] groupings.     

Influence of MeF2 (Me = Mg, Ca, Sr, and Ba) on the electrical properties of glasses in the MeF2-Na2B4O7 system

Glasses in the MeF₂-Na₂B₄O₇ (Me = Mg, Ca, Sr, and Ba) system have been synthesized. It is shown that the glass formation is observed at a MeF₂ content of up to 40 mol %. The influence of the MeF₂ content on the electrical conductivity and the fluorine concentration in the glass bulk is examined. From the analysis of the concentration dependence of the electrical conductivity with due regard for the fluorine content, it is concluded that the glass structure is predominantly built up of the polar groupings Na⁺[BO_4/2]^-, Na⁺[F-BO_3/2], Me _1/2 ²⁺ [BO_4/2]⁻, Me _1/2 ²⁺ [F⁻BO_3/2], [MeF_4/2], and [MeF_6/3] and the BO_3/2 nonpolar structural-chemical units. The electricity transport is governed by the migration of sodium ions formed upon dissociation of the Na+[BO_4/2]^-and Na+[F^-BO_3/2] groupings. An increase in the MeF₂ content leads to a decrease in the total concentration of sodium ions, a decrease in the Na⁺[BO_4/2]^- concentration, and an increase in the Na⁺[F^-BO_3/2] concentration. Upon introduction of MeF₂ up to ∼20 mol %, the fluorine losses during the synthesis are caused by the dehydration of glass melt. An addition of 20–25 mol % MeF₂ brings about the saturation of the glass by the [F^-BO_3/2]-type structural units, so that the fluorine concentration reaches a saturation in the structures of calcium-, strontium-, and barium-containing glasses and increases in magnesium-containing glasses, owing to the formation of the [MgF+_6/3] groupings.     

The nature of current carriers and electric conductivity in the PbCl2-2PbO ? SiO2 glasses

The nature of current carriers is revealed and the concentration dependence of the true transport numbers of chlorine ions η is studied by the Tubandt method in glasses of the PbCl₂-2PbO · SiO₂ system. It is demonstrated that, in glasses containing up to ∼20 mol % PbCl₂, the electricity transport occurs through protons and chlorine ions. At [PbCl₂] ≥ 20 mol %, the electric current is carried primarily by the chlorine ions. The known crystalline compounds in the PbO-PbCl₂ system are synthesized, and the temperature dependences of their electric conductivity are investigated for the first time. It is found that the introduction of PbCl₂ into PbO is accompanied, first, by an increase in the electric conductivity (to a PbCl₂ mole fraction of ∼0.5), and, then (when PbCl₂ single crystals are formed), by its decrease. The temperature-concentration dependence of the electric conductivity for glasses in the PbCl₂-2PbO · SiO₂ system is interpreted in terms of structural-chemical microinhomogeneity of the glass structure due to the selective interaction of components during the glass synthesis.     

The nature of current carriers and electric conductivity in the PbCl2-2PbO • SiO2 glasses

The nature of current carriers is revealed and the concentration dependence of the true transport numbers of chlorine ions η is studied by the Tubandt method in glasses of the PbCl₂-2PbO · SiO₂ system. It is demonstrated that, in glasses containing up to ∼20 mol % PbCl₂, the electricity transport occurs through protons and chlorine ions. At [PbCl₂] ≥ 20 mol %, the electric current is carried primarily by the chlorine ions. The known crystalline compounds in the PbO-PbCl₂ system are synthesized, and the temperature dependences of their electric conductivity are investigated for the first time. It is found that the introduction of PbCl₂ into PbO is accompanied, first, by an increase in the electric conductivity (to a PbCl₂ mole fraction of ∼0.5), and, then (when PbCl₂ single crystals are formed), by its decrease. The temperature-concentration dependence of the electric conductivity for glasses in the PbCl₂-2PbO · SiO₂ system is interpreted in terms of structural-chemical microinhomogeneity of the glass structure due to the selective interaction of components during the glass synthesis.     

Structure and Electrical Properties of Iron Borosilicate Glasses

Glassesofnominal composition 25SiO₂- 30Na₂O-2Al₂O₃-x Fe₂O₃-(43- x)B₂O₃ (x = 1 to 6 mol%) were prepared by the ordinary melt quenching technique. The influence of Fe₂O₃ substitution at the expense of B₂O₃ on structure and electrical conductivity of sodium borosilicate glasses was investigated. The conductivity was found to increase with increasing Fe₂O₃ content. A double channel conduction mechanism was introduced to explain the electrical conductivity measurements. Moreover, the activation energy decreases considerably in the temperature range from 473 to 773 °K. The activation energies of conduction in various temperature regions were calculated. The conduction was best described by sodium ion migration and hopping between the two valence states of iron. FTIR absorption spectra in the spectral range 1600-400 cm^?1 were measured and a deconvolution analysis technique (DAT) using Gaussian peaks was introduced to analyze the studied glasses. Different characteristic bands were observed and attributed to different types of borate besides silicate vibrational groups.     

Synthesis and properties of the water-soluble self-acid-doped polypyrrole: poly[4-(3-pyrrolyl)butanesulfonic acid]

The water-soluble polypyrrole, poly[4-(3-pyrrolyl)butanesulfonic acid] (P3PyBSH), in which the β-position of pyrrole ring is substituted with n-butanesulfonic acid group, is synthesized by oxidation polymerization of 3PyBSNa followed with an ion-exchange of Na⁺ with H⁺. It can be cast into free-standing film from its aqueous solution and has a conductivity of 4.0×10⁻⁴ S/cm, higher than that of its sodium salt (5.5× 10⁻⁶ S/cm) by about 2 orders. The increase in conductivity is attributed to the self-doping by the protons originally on the side chains as supported by the absence of the anion FeCl₄ ⁻ (which generates during the polymerization) and the presence of polaron and bipolaron characteristics in its UV-Vis and IR spectra.     

Influence of rare earth additives and boron component on electrical conductivity of sodium rare earth borate glasses

Sodium rare earth borate glasses (Na₂O)_35.7(RE₂O₃)_7.2(B₂O₃)_57.1 (RE = Sm, Gd, Dy, Ho, Y, Er, and Yb), were prepared from a mixture of Na₂CO₃, RE₂O₃ and B₂O₃, and their properties as an Na⁺ ionic conductor were investigated. Density increased with increasing atomic weight of RE. Crystallization temperature and crystal melting temperature of the present borate system was lower than that of the previously reported silicate and germanate system. Results of the ¹¹B NMR measurement suggested that half of all boron atoms are coordinated by four oxide ions to give a [BO₄] tetrahedral unit and the others are coordinated by three oxide ions to give a [BO₃] planar triangular unit. The electrical conductivity slightly decreased with increasing the ionic radius of RE³⁺. (Na₂O)_35.7(Y₂O₃)_7.2(B₂O₃)_57.1 glass exhibited the electrical conductivity which is about one order of magnitude lower than those of the previously reported (Na₂O)_35.7(Y₂O₃)_7.2(SiO₂)_57.1 and (Na₂O)_35.7(Y₂O₃)_7.2(GeO₂)_57.1 glasses. It was assumed that this lower electrical conductivity is due to the lower content of Na⁺ ions as conduction species in the former glass, compared with the latter two glasses.     

Water vapor and oxygen permeability of wax films

The water vapor (WVP) and oxygen (O₂P) permeabilities of beeswax (BW), candelilla wax (CnW), carnauba wax (CrW) and microcrystalline wax (MW), formed as freestanding films, were determined. CnW and CrW both had small values for O₂P (0.29 and 0.26 g·m⁻¹·sec⁻¹·Pa⁻¹ × 10⁻¹⁴, respectively), which are less than half the value for high-density polyethylene and about a decade greater than the value for polyethylene terephthalate. O₂P values for BW and MW were about 6−9× greater than those of CnW and CrW. WVP of CnW was 0.18 g·m⁻¹·sec⁻¹·Pa⁻¹ × 10⁻¹², which is about one-half the value for CrW and MW and about one-third the value for BW. The WVP of CnW was somewhat less than that of polypropylene and somewhat greater than that of high-density polyethylene. Differences in permeabilities among the wax films are attributed mainly to differences in chemical composition and crystal type as determined by X-ray diffraction.     

Refractive index and compressibility of the KAlSi<Subscript>3</Subscript>O<Subscript>8</Subscript> glass at pressures up to 6.0 GPa

The refractive index of potassium aluminosilicate glass of the KAlSi₃O₈ composition in the pressure range up to 6.0 GPa has been measured using a polarizing interference microscope and an apparatus with diamond anvils. The changes in the relative density, which characterize the compressibility of the K₂O · Al₂O₃ · 6SiO₂ glass, have been estimated in the pressure range under investigation from the measured refractive indices within the framework of the theory of photoelasticity. The results have been compared with the data previously obtained for the Na₂O · Al₂O₃ · 6SiO₂ glass. Although the molar contents of Al₂O₃ and M ₂O (where M = K or Na) are identical in these glasses, the KAlSi₃O₈ glass exhibits a higher compressibility, which agrees with the lower degree of depolymerization of this glass as compared to that observed in the NaAlSi₃O₈ glass. The pressure derivative of the bulk modulus K′ _t , which is calculated from the Birch-Murnaghan equation for the KAlSi₃O₈ glass (K′ _t = 7–9), is higher than that for the NaAlSi₃O₈ glass (K′ _t = 5.5–6.0). An increase in the pressure derivative of the bulk modulus K′ _t upon replacement of the Na⁺ cations by the K⁺ cations is explained by the inhibition of compression of the large K⁺ cations, which are located in cavities and have a considerably larger orbital radius than the Na+ cations. This manifests itself in the fact that the curves describing the dependences of the change in the relative density (d − d0)/d (compressibility) on the pressure P for the KAlSi₃O₈ and NaAlSi₃O₈ glasses converge at pressures above 4.0 GPa.     

Diffusion of cations in sodium-potassium and sodium-barium silicate melts

Diffusion coefficients of sodium and potassium ions in molten glasses with the composition (25 ? x)Na₂O · xK₂O · 75SiO₂ have been determined by the sectioning method with measurement of the residual activity ²²Na and ⁴²K isotopes. Diffusion of sodium and ¹³³Ba ions has been studied in melts of the (30 ? x)Na₂O · xBaO · 5Ga₂O₃ · 65SiO₂ system. It has been found that the concentration dependences of diffusion characteristics in melts containing alkali and alkaline-earth cations principally differ from the regularities diffusion in dialkali melts.     

Dissolution mechanism of colemanite in sulphuric acid solutions

Boron compounds are very important raw materials in many branches of industry and their uses have been increasing and expanding continuously. Colemanite, one of the most common boron minerals, has a monoclinic crystal structure with a chemical formula of 2CaO·3B₂O₃·5H₂O and is used usually in the production of boric acid. The present study concerns and investigation of the dissolution mechanism of colemanite in H₂SO₄ solution and the effect of acid concentration, the effect of SO₄⁻² ion on the dissolution process, using H₂SO₄, HCI+H₂SO₄ and H₂SO₄+Na₂SO₄ solutions. The analysis of the experimental data shows that increasing H₃O⁺ acid concentration increased the dissolution rate, but increasing SO₄⁻² concentration reduced dissolution rate because of the precipitation of a solid film of CaSO₄ and CaSO₄·H₂O.     

The Effects of Concentration, Relative Permittivity and Temperature on the Transport Properties of Sodium Polystyrenesulphonate in Methanol–Water Mixed Solvent Media

Precise measurements on the electrical conductivity of solutions of sodium polystyrenesulphonate in methanol–water mixed solvent media containing 8, 16, 25, and 34 wt.% of methanol at 308.15, 313.15, 318.15, and 323.15 K are reported. The degree of substitution of sodium polystyrenesulphonate used was 1, and the concentrations were varied from ∼2.0 × 10⁻⁴ to ∼4.0 × 10⁻³ monomol l⁻¹. The results showed a slight and monotonous increase in the equivalent conductivity with decreasing polyelectrolyte concentration. The applicability of the Manning’s theory for salt-free polyelectrolyte solution was examined and a major discrepancy against the theory was observed. The calculated values of the equivalent conductivity deduced on the basis of this theory were found to be lower than the experimental ones. Possible reasons for this discrepancy have been discussed. The effects of the temperature and relative permittivity of the medium on the equivalent conductivity were also investigated. Estimation of the fractions of uncondensed counterions provides important insight regarding the solution behavior of the polyelectrolyte in methanol–water mixtures.