Electrical Conductivity of Alkali-Doped Zr-Ba-La-Al Fluoride Glasses

The effect of alkali ion identity on the dc electrical conductivity of alkali-doped Zr-Ba-La-Al fluoride glasses containing 5 mol% MF, where M is Li, K, or Cs, was measured. The electrical conductivity increases in the order Li < K < Cs. This trend is the reverse of that found for typical oxide glasses. Results support the contention that these glasses are anion conductors.     

Electrical Conductivity of Silver Vanadium Tellurite Glasses

We have investigated mixed electronic-ionic conduction in 0.5[ x Ag₂O·(1 − x )V₂O₅]–0.5TeO₂ glasses, where the Ag₂O amount varies over a range of 5–40 mol%. The glass samples have been prepared by quenching the melt. The ac conductivity has been measured at frequencies from 10 Hz to 100 kHz and temperatures of 300–425 K. The data indicate that the conduction mechanism changed from being predominantly electronic to ionic for Ag₂O contents of >27.5 mol%. This transition is due to the change in glass structure, which affects both electronic- and ionic-transport properties. The electronic dc conductivity results have been analyzed in terms of a small polaron-hopping model.     

Structural,Dielectric and AC Conductivity of Multicomponent Borotellurite Glasses

Glass Physics and Chemistry - Structural, dielectric and conductivity of multicomponent borotellurite glasses have been thorougly investigated. Noncrystallinity confirmed through XRD and structural...     

Some Structural and Electrical Properties of Lithium Silicate Glasses

Dielectric measurements, analyzed in terms of the Maxwell-Wagner-Sillars theories of inhomogeneous dielectrics, have been used to investigate the phase-separation characteristics of various lithium silicate glasses. Such measurements are shown to provide evidence of the continuous or discontinuous nature of separated phases and to allow estimates of their shape factors and concentrations. The results indicate that dielectric measurements are particularly useful in following phase-separation processes in glasses from the initial to the final stages.     

Tracer Diffusion and Electrical Conductivity in Sodium-Rubidium Silicon Sulfide Glasses

The tracer diffusion coefficients of ²²Na and ⁸⁶Rb and electrical conductivity were measured in a series of 0.56(Na, Rb)₂S.0.44SiS₂ glasses as a function of the Rb/Na ratio and temperature. The data were used to calculate the Haven ratio as a function of the Rb/Na ratio. The Haven ratio at 149.6°C increases from ∼0.3 in single-alkali glasses to ∼0.80 for intermediate compositions. The results are consistent with a single jump mechanism involving jumps of alkali ions between unoccupied sites. The observed correlation effects arise through interactions between alkali ions and charge-compensating centers in the glass network. The charge-compensating centers are thought to correspond to non-bridging oxygen ions in some oxide glasses and to nonbridging sulfur ions in sodium-rubidium silicon sulfide glasses.     

Structural Characteristics and Electrical Conductivity of Vanadium-doped lithium Ultraphosphate Glasses

Glasses of the 33.5Li₂O-66.5P₂O₅-xV₂O₅ (mol. %) system with (0 ≤ x ≤ 5) were prepared by the normal melting and annealing technique. Their physical and spectroscopic properties such as X-ray powder diffraction (XRD), density, infrared spectroscopy and electrical conductivity were investigated. The composition dependent density shows an initial decrease at 0.1 mol.% of V₂O₅ followed by an increase in density with further addition of the V₂O₅ content. The structure of these glasses has been studied by recording the Fourier-transform infrared spectroscopy (FTIR) over the range 400–1800 cm^?1. Vibrational modes are assigned to different types of phosphate groups in the glass network. The temperature (333–452 K) and composition dependence of direct current (DC) electrical conductivity were measured. The electric conductivity is observed to increase with the first addition of vanadium oxide reflecting the presence of V⁴⁺ions that take part within modifying positions in the glass network .Then, the electric conductivity is found to decrease with the further increase in the content of V₂O₅ up to 5 mol.% reflecting the formation of V⁵⁺ions that take part as network forming positions in the glass network. The variations in density and electrical conductivity with V₂O₅ content are discussed in terms of changes in the glass structure.     

Effect of Atmosphere on the Electrical Conductivity of Sodium Tungstophosphate Glasses

The dc electrical conductivity of sodium tungstophosphate glasses was measured as a function of glass composition, melting history, and ambient atmosphere. The color of the glasses was a strong function of both glass composition and melting history. The electrical conductivity was found to be strongly dependent upon the concentration of protons in the surrounding atmosphere. The colorless glasses were found to be electrochromic only so long as protons were present in the atmosphere. A model is suggested to explain these results.     

Effect of Water Content on the Electrical Conductivity of Sodium Trisilicate Glasses

The effect of variations in water content on the direct-current electrical conductivity of Na₂O · 3SiO₂ glass was measured. Increasing the water content of this glass from 10 to 500 wt ppm of H₂O results in an increase in the resistivity of a factor of 2 to 3. The increase in resistivity is accompanied by an increase in the activation energy for conduction. Increasing resistivity with increasing water content is attributed to decreasing molar volume. Under identical annealing conditions, "wetter" glasses relax to a smaller molar volume (greater density) because of the presence of a larger number of "terminal" hydroxyl species that allow structural relaxation to continue to lower temperatures.     

Morphological and Electrical Conductivity of Novel Nano Lithium Phthalocyanine Complexes

Novel nano-filament lithium phthalocyanine (LiPc) complexes with different concentrations of Li ⁺ ions have been prepared successfully via the urea fusion technique. Spectrophotometric measurements such as XRD and SEM are used to characterize the obtained nano-filament complexes. The behavior of electrical conductivity (DC and AC) for the prepared complexes at frequency range 0.1 KHz – 5 MHz and temperature 298 K ≤ T ≤ 423 K is presented. The conduction mechanism is suggested to be a result of thermal hopping of the activated electrons while at low frequency range the electrons may tunnel through the nanoparticles of LiPc complexes. The activation energies of DC-conductivity were calculated from the Arrhenius plot and ranged from 0.314 eV to 1.243 eV. These values show that the rate of electron transport depends on temperature within these ranges.     

DC and AC Conductivity Study of Basalt Glasses Containing High Concentrations of Na+ Ions

Different glass samples prepared from Egyptian basalt with different Na₂O content according to the composition [(100-x) basalt + x Na₂O], where x = 10, 15, up to 35 mol%. The samples mixtures were melted at 1300 °C for 2 h. Each sample will be recognized from its sodium to basalt (S/B) ratio. The sample of 0.54 ratio exhibits a slight crystalline phase. As S/B ratio was increased, the density decreased gradually while the molar volume increased, and the pure amorphous nature was confirmed by comparing the experimental and the empirical density and molar volume values. The electrical conductivities, DC and AC, were found to increase as the (S/B) ratio was gradually increase up to 0.33, then the samples showed approximate stable value up to the sample of 0.54 ratio. While the activation energy showed gradual decrease up to 0.33 ratio, then it exhibits nearly a stable value. The activation energy values indicated that all the studied samples behave like semiconductors. It appeared also from the AC conductivity results that the relation of the s-factor with the sample temperature showed that the conduction mechanism of these samples obeys the correlated barrier hopping (CBH) model. The structure of the same samples was studied in our previous work by XRD, FTIR and Mössbauer spectrometer.

     

Thermal Conductivity of Silicate and Borate Glasses

Thermal conductivities of silicate and borate glasses were determined at 30°C by steady-state methods. From the experimental data, factors representing the contribution of individual oxides (on a weight-percent basis) were calculated by the least-squares method. The experimental thermal conductivities and those calculated from the factors obtained agree fairly well.     

Electrical Conductivity Studies on Individual Conjugated Polymer Nanowires: Two-Probe and Four-Probe Results

Two- and four-probe electrical measurements on individual conjugated polymer nanowires with different diameters ranging from 20 to 190 nm have been performed to study their conductivity and nanocontact resistance. The two-probe results reveal that all the measured polymer nanowires with different diameters are semiconducting. However, the four-probe results show that the measured polymer nanowires with diameters of 190, 95–100, 35–40 and 20–25 nm are lying in the insulating, critical, metallic and insulting regimes of metal–insulator transition, respectively. The 35–40 nm nanowire displays a metal–insulator transition at around 35 K. In addition, it was found that the nanocontact resistance is in the magnitude of 10⁴ Ω at room temperature, which is comparable to the intrinsic resistance of the nanowires. These results demonstrate that four-probe electrical measurement is necessary to explore the intrinsic electronic transport properties of isolated nanowires, especially in the case of metallic nanowires, because the metallic nature of the measured nanowires may be coved by the nanocontact resistance that cannot be excluded by a two-probe technique.     

Dc Conductivity of Ge-S-Ag and As-S-Ag Glasses

The dc conductivity in GeS₂-GeS-Ag₂S and As₂S₃-Ag₂S glasses was measured over the range – 20° to 80°C using an electrode of 1 at.% Ag amalgam to avoid polarization. The room-temperature conductivity varies with increasing Ag₂S content from 10⁻¹⁵ to 10⁻⁴Ω⁻¹ cm⁻¹ for GeS₂-GeS-Ag₂S glasses and from 10⁻¹⁶ to 10⁻⁵Ω⁻¹ for As₂S₃-Ag₂S glasses. Also, the transport numbers of Ag ions in the glasses were measured by the Hittorf and emf methods. The results show that all glasses in both systems, except for compositions with low Ag₂S contents, are purely ionic conductors because of the presence of Ag ions, so that they may be regarded as solid electrolytes.     

Thermal Conductivity of Lead Borate Glasses

Thermal conductivity of glasses in the system PbO-B₂O₃ at 30°C were determined by steady-state methods. The values decrease progressively with increasing PbO content. The experimental thermal conductivities and those calculated from factors representing the contributions of individual oxides (on a weight percent basis) agree fairly well.     

Crystallization Kinetics of Lithium Orthosilicate Glasses

The formation of crystalline Li₄SiO₄ and Li₂SiO₃ from lithium orthosilicate glasses has been studied by means of in situ high-temperature X-ray diffraction. The first phase that crystallizes from the glass could not be identified, but was followed by the transformation to crystalline orthosilicate and metasilicate. Orthosilicate formation was tracked at temperatures between 600° and 650°C, whereas at higher temperatures, the formation of a small amount of crystalline metasilicate occurs. The kinetics of the initial phase of both crystallization processes are described by the Avrami–Erofeev equation, resulting in activation energies of 90 kJ/mol for the formation of the unidentified phase, and 68 kJ/mol for the formation of Li₄SiO₄. The rate constant for the crystallization of the unidentified phase is 0.014 s⁻¹ at 510°C, equaling that of the orthosilicate formation at 630°C. After isothermal heat treatment for 100–800 s, depending on temperature, 80%–95% of the sample is crystallized and further crystallization is controlled by diffusion in both cases.     

Gamma Radiation Shielding and Mechanical Studies on Highly Dense Lithium Iron Borosilicate Glasses Modified by Zinc Oxide

Silicon - Five glass samples of a new zinc-iron lithiumborosilicate (LBSFZ) with the chemical formula 64.8B2O3–8.5SiO2–1.5Fe2O3 –&nbsp;(25.2 − x)Li2O - x ZnO...     

Thermal Conductivity of Infrared Transparent Chalcogenide Glasses

Chalcogenide glasses exhibit low thermal conductivities on the order of 10^-3 W cm^-1K^-1. Since many of these glasses are transparent in the infrared, the photon contribution to the apparent thermal conductivity of these materials can be significant even at relatively low temperatures, The temperature-dependent thermal conductivity of Ge₂₈ Sb₁₂ Se₆₀ was measured over the range 175 to 475 K and a simplified approach is presented to correct the data for radiation (photon) effects. In addition, room-temperature thermal conductivities of 13 other glass compositions were measured. The phonon conductivities agreed well with simple Debye theory predictions after the radiation contributions were eliminated.     

Electrical Resistivity of Titanium-Containing Glasses

Titanium-containing glasses were prepared by fusion of a base glass (BaO·B₂O₃SiO₂) and TiO₂ and/or Ti₂O₃ in Ar. Their resistivities did not vary with melting time and temperature. Interaction of Ti⁴⁺ and Ti³⁺ in the glasses was deduced by spectroscopy, but the valence states in the batch compositions were preserved in the glasses, according to the chemical analysis. Glasses containing either Ti⁴⁺ or Ti³⁺ had very high resistivities, whereas the glass prepared by melting a mixture of a Ti⁴⁺-containing and a Ti³⁺-containing glass had much lower resistivity. All results confirmed the possibility of controlling the resistivity by batch composition for these glasses.