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Phosphate glasses with the compositions 40P 2 O 5 –10MnO 2 –(50– x)Li 2 O– x K 2 O (x = 5, 15, 25, 35, and 45 mol%) have been prepared by the conventional melt quenching technique. X-ray diffraction (XRD) patterns confirmed the amorphous nature of the samples. Elemental analysis of the glasses has been performed by X-ray fluorescence (XRF) spectroscopy. The mixed alkali effect (MAE) on the structural, physical, and electrical properties of the present glassy systems has been investigated. A nonlinear variation in density upon the incremental replacement of Li 2 O by K 2 O corroborated the operation of an MAE in modulating the structural properties. Fourier-transform infrared (FTIR) spectra revealed that the structures are mainly composed of metaphosphate and pyrophosphate units. Differential scanning calorimetry (DSC) has been performed to investigate the thermal behavior of the samples and to determine their glass transition temperatures (T g). DC electrical conductivity increased with increasing temperature, which proved the semiconducting nature of the glasses. It was found that ionic conductivity plays a greater role in determining the electrical properties of the systems than electronic conductivity. [Display omitted] • X-ray diffraction patterns confirmed the amorphous nature of the samples. • Nonlinear variation of the structural parameters was explained using Stevels' theory. • Replacement of Li by K ions leads to a change in the formation of nonbridging oxygen. • The MAE was clearly observed in the electrical properties. [ABSTRACT FROM AUTHOR]

In this research, we performed experimental investigations of the influence of copper presence on hardness of arsenic triselenide (As2Se3)–arsenic triiodide (AsI3) pseudobinary glasses. The samples belong to the group of chalcogenide glasses, that, when compared with oxide glasses, can be synthesized much more easily in a wide variety of compositions, allowing also fine-tuning of their properties. Here, presence of iodine (I) facilitates glass formation, whereas addition of copper (Cu) creates possibility for interesting optoelectronic properties. As it is important to study mechanical properties of materials with respect to their fabrication and manipulation, we report results of instrumented indentation testing (IIT) of bulk samples of Cux[(As2Se3)0.9(AsI3)0.1]100−x with x = 5, 10, 20, and 25 at.% of Cu. This technique enables fast determination of indentation hardness, hardness value according to Vickers and indentation modulus directly from the indentation load–displacement curves. It was shown that all these parameters increase linearly with the increase of copper content. Improvement of the mechanical properties justifies the addition of Cu into the glass matrix. [ABSTRACT FROM PUBLISHER]

Abstract: The deeper understanding of the factors that affect the dimensionless figure of merit, ZT, and the use of new synthetic methods has recently led to the development of novel systems with improved thermoelectric performances. Albeit up to now with ZT values lower than the conventional bulk materials, semiconducting glasses have also emerged as a new family of potential thermoelectric materials. This paper reviews the latest advances on semiconducting glasses for thermoelectric applications. Key examples of tellurium-based glasses, with high Seebeck coefficients, very low thermal conductivities and tunable electrical conductivities, are presented. ZT values as high as 0.2 were obtained at room temperature for several tellurium-based glasses with high copper concentrations, confirming chalcogenide semiconducting glasses as good candidates for high-performance thermoelectric materials. However, the temperature stability and electrical conductivity of the reported glasses are still not good enough for practical applications and further studies are still needed to enhance them. [Copyright &y& Elsevier]

Abstract: The dc conductivity of semiconducting cobalt–phosphate glasses has been measured at temperatures ranging from 213 to 530K. Four bulk samples of CoO–P2O5 glasses of different compositions were produced by melting dry mixtures of analytical reagent grades of CoO and P2O5 at temperatures between 1200–1250°C for 2h using a press-quenching method from glass melt. Samples were annealed at 400°C for 1h. The dc conductivity was found to be dependent on the CoO content in the glass. At temperatures from 213 to 444K, however, both Mott''s variable-range hopping (VRH) and the Greaves'' intermediate range hopping models are found to be applicable. VRH at this range of temperatures is attributed to large values of the disorder energy of these glasses. [Copyright &y& Elsevier]

SrO-borovanadate glasses with the nominal composition (V2O5)z(SrO)0.2( B2O3)0.8-z, 0.4≤z ≤0.8 were studied by direct current (DC) electrical conductivity, inductively coupled plasma (ICP) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and X-ray-powder-diffraction (XRD). These glasses were prepared by a normal quench technique and the actual compositions of the glasses were determined by ICP spectroscopy. XRD patterns confirm the amorphous nature of the present glasses. The temperature dependence of DC electrical conductivity of these glasses has been studied in terms of different hopping models. The IR results agree with previous investigations on similar glasses and it has been concluded that similar to SrO-vanadate glasses, metavandate chainlike structures of SrV2O6 and individual VO4 units also occur in these SrO-borovanadate glasses. The SrV2O6 and VOn polyhedra predominate in the low B2O3 containing SrO-borovanadate glasses as the B substitutes into the V sites of the various VOn polyhedra and only when the B2O3 concentration exceeds the SrO content do BOn structures appear. This qualitative picture of three distinct structural groupings for the Sr-vanadate and Sr-borovanadate glasses is consistent with the proposed glass structure on previous IR and extended X-ray absorption fine structure (EXAFS) studies on these types of glasses. The conductivity results were analyzed with reference to theoretical models existing in the literature and the analysis shows that the conductivity data are consistent with Mott's nearest neighbor hopping model. However, both Mott VRH and Greaves models are suitable to explain the data. Schnakenberg's generalized polaron hopping model is also consistent with the temperature dependence of the activation energy, but the various model parameters such as density of states, hopping energy obtained from the best fits were found to be not in accordance with the prediction of the Mott model. [ABSTRACT FROM AUTHOR]

Abstract: Heavy metal based oxide glasses of compositions xMoO3·(40− x)PbO·60B2O3 have been prepared by the standard melt-quenching technique. The various properties such as the glass transition temperature (T g), density, theoretical optical basicity, IR and DC conductivity have been studied. Amorphous nature of the present system was estimated by XRD patterns. The decrease in the density (d) and glass transition temperature (T g) is due to the lower degree of cross-bonding between the Molybdenum and non-bridging oxygen ions resulting in a weakening of glass network. The structural changes in these glasses have been monitored by IR spectroscopy. The effect of temperature on the DC conductivity has been measured in the temperature range 473–623K for all the compositions. The existence of a polaronic hopping conduction mechanism between Mo5+ and Mo6+ cations suggested that these glasses act as purely electronic semiconductor glasses. The values of theoretical optical basicity of these glasses have also been presented. [Copyright &y& Elsevier]

Abstract: CeO2–B2O3 glasses having a broad range of compositions, prepared by a press-quenching method from glass melts, were studied for DC conductivity. The conductivity at 583K (1000/T=1.715K−1), ln σ 583, increases by about 16% in the composition regime 20–50mol% CeO2 while in the composition range 50–60mol% CeO2, ln σ 583 decreases by about 28%. The behavior of ln σ 583 with composition can be interpreted in terms of the changes in the high-temperature activation energy W and the hopping distance, R. Between 20 and 50mol% CeO2, increasing the mechanical strength and cross-linking of the glass network results in decreasing the polaron hopping energy, W H. At higher concentrations, the breaking of the 3D network observed to be probable for these glasses may increase the disorder energy, W D. The conduction mechanism is found to be non-adiabatic in nature for glasses investigated. Mott''s model for the small polaron hopping conduction between nearest-neighbors gives unreasonable values for the Ce–Ce distance and the phonon frequency of the lattice vibrations. The increase in the conductivity with temperature can be interpreted in terms of the Schnakenberg model for optical multiphonon assisted hopping process at high temperatures and single optical phonon process at the lower ones. This model gives reasonable values for the phonon frequency of the lattice vibrations, the polaron hopping energy, and slightly higher values of W D. [Copyright &y& Elsevier]

Abstract: Mössbauer Effect (ME) spectroscopy, density and molar volume as well as electrical transport measurements were employed to investigate the glass system: (70− x) mol% B2O3· (x) mol% Pb3O4·10mol% Fe2O3·20mol% Na2O [with 0≤ x ≤35]. Both ME and density were measured at room temperature but conductivity measurements were carried out in the temperature range from 320 to 560K at four fixed frequencies [0.12, 1, 10 and 100kHz]. The ME results showed that, in the lead free sample only, about 80.8% of the total iron act mostly as glass network modifier (GNM), while the rest precipitated as α-Fe2O3. As lead oxide was just introduced into the glass, it assists to dissolve all iron ions through the glass network and iron ions start directly to occupy glass network former (GNF) positions. Both the density and the oxygen molar volume increased as lead oxide were increased. It was found also that the ac conductivity [σ (ω)] is higher than the dc conductivity (σ dc ) at low temperatures, whereas at high temperatures, σ (ω) approaches σ dc at all frequencies. These results were explained in terms of the percolation path approximation (PPA) model, due to the macroscopic inhomogenity of the glass network. A good agreement has been obtained between the experimental results and the theoretical fitting of PPA at low frequencies, while at high frequencies the results showed slight deviation. The dielectric constant and the dielectric loss were found in good agreement with the theoretical fitting of Cole–Cole equation. [Copyright &y& Elsevier]

Abstract: The I–V characteristics and the electrical switching behavior for a bulk glass system of the composition (80-x)% V2O5–(x)% SrO–20% FeO [15≤x≤40], have been investigated at different temperatures. The studied glasses are found to exhibit a current controlled-negative resistance behavior of the threshold switching mode and the results are discussed in terms of the electrothermal model. It was concluded that the threshold voltage increased as SrO was gradually increased while it decreases when the temperature was increased. The activation energy for switching was found to decrease with the increase of SrO content. The field lowering coefficient β which was calculated experimentally appeared in agreement with that calculated from Poole–Frenkel equation βPF. [Copyright &y& Elsevier]

In this study, V 2 O 5 , P 2 O 5 and B 2 O 3 oxide compounds, traditional glass formers, were used simultaneously and dark Cu-doped VPB glasses were successfully synthesized. Glass composition was determined as 46V 2 O 5 –46P 2 O 5 –(8-x)B 2 O 3 –xCuO (mol%) and undoped and Cu-doped glasses were synthesized with melt-quenching method. By changing the CuO and B 2 O 3 in the structure, it was investigated how the properties of the synthesized glasses change with the addition of transition metal oxide to the structure. Firstly, the physical properties of the synthesized glasses were determined such us density and molar volume. X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analyzes were performed to observe the changes of transition metal oxide additive to the glass structure. The optical band gaps and Urbach energies of the glass series that absorb the visible region and whose transmittance starts at approximately 1750 nm were calculated by using Tauc plot method. Finally, the thermal properties of the synthesized glasses were performed via differential scanning calorimetry (DSC). • Copper-doped vanadium phosphate boron (VPB) glasses were synthesized by using traditional melt-quenching method. • The densities of the synthesized Cu-doped VPB glasses have increased, while the molar volume values have a decreasing trend. • The transmittance and absorbance characteristics were measured and X-ray diffraction and Raman analyses were performed. • Direct and indirect optical band gaps, and Urbach energies of synthesized glasses were calculated. • Glass stability (GS) parameters were calculated using four different method. [ABSTRACT FROM AUTHOR]

Five bulk samples of ternary CoO–NiO–P2O5 glasses were prepared by a press-quenching method from glass melt. TEP measurements have been made on annealed samples using a specially design sample holder in the temperature range 303–530 K. The temperature difference between upper and lower surfaces was maintained between 5 and 10 K. The investigations provide information on the polaron formation and the disorder energy due to random fields. TEP was found to be independent of temperature. [Copyright &y& Elsevier]