Thermal, Structural, and Dielectric Properties of Cu-Doped Ge-S Glasses

Glasses of GeS_1.5+y at.% Cu and GeS 1.375 +z at.% Cu were analyzed by DTA. For concentrations y ≊2.5 and z ≊4, new exothermic transformations and an initial small endothermic effect appear. All these transformations occur below the glass transition temperature of the original Ge:S glass, Analysis by X-ray and electron diffraction showed that this devitrification process is connected with crystallization of a Cu₂GeS₃ phase. Electron transmission microscopy showed that this crystalline phase is dispersed in a glassy matrix as disconnected aggregates with irregular symmetry. Near the maximum copper concentration y ≊5, z ≊6) at the boundary of the glass-forming region, there is one additional exothermic transformation in the system GeS_1.5+y at.% Cu and two in the system GeS_1.375+z at.% Cu, one of them corresponding to crystallization of the Cu₃GeS₄ phase. X-ray diffraction patterns of the crystalline phases are shown. The spectrum of ionic thermocurrents in such glassyceramic material shows a new peak at 120 K which is probably related to interfacial polarization associated with the crystalline phase-glassy matrix boundary.     

Properties and Structure of Lead Halosilicate Glasses

The glass transformation temperature, thermal expansion coefficient, dc electrical conductivity, and IR transmission have been measured for four series of lead halosilicate glasses of the general composition (65– x )PbO· x PbX₂·35 SiO₂ (X=F, Cl, Br, I). Although results of these and other measurements suggest that the halide ions play similar structural roles in the glass, there appear to be significant differences in physical property behavior between glasses containing F⁻ anions and those containing the other three halide anions. These results are explained by a proposed model incorporating both bridging and nonbridging halide species.     

Properties and Structure of Lead Fluorosilicate Glasses

An extensive glass-forming region has been determined for the lead fluorosilicate system. These glasses have a very high anionic (fluorine) conductivity. The value of 2 x 10_-4ω_-1.cm_-1 at slightly less than 200°C found for one glass is the highest anionic conductivity reported to date in a glass. Glass transition temperatures, thermal expansion coefficients, and UV-visible spectra were also measured. Results of these measurements and melt-history studies will be discussed and related to a proposed structural model for the lead fluorosilicate glasses.     

Properties and Structure of Lanthanum Borate Glasses

Glass formation limits were determined for the lanthanum borate glasses. Stable immiscibility prevents the formation of clear glasses over the range 0 to 20 mol% La₂O₃, but excellent quality glasses could be formed between 20 and 28 mol% La₂O₃. Data are reported for the density, refractive index, thermal expansion coefficient, glass transformation and dilatometric softening temperatures, transformation range viscosity, helium permeability, and chemical durability of these glasses. A limited Raman and infrared spectroscopy study suggests that lanthanum plays a similar structural role in these glasses and in the related crystals.     

Structure and Properties of Long-Wavelength-Transmitting Halide Glasses

The lower halides of zinc, namely, ZnCl₂, ZnBr₂, and ZnI₂, may act as network formers in glasses that also contain modifying alkali halides such as KCI, KBr, KI, NaI, or CsI. Compositions which contain only Br⁻ or I⁻ anions are of particular interest because of their extended infrared transmission, which includes the ∼10-μm region, in addition to full visible transparency. A series of modified zinc halide glasses were prepared and characterized by differential scanning calorimetry, middle and far Fourier transform infrared spectroscopy, and polarized Raman spectroscopy. T _g values were characteristically low, around 40°C. Bulk glass infrared transmission up to 15 to 20 μm was recorded. The most probable glass structures are discussed and compared to oxide glass models. An attenuation of  0.001 dB/km has been projected as a possible intrinsic minimum for optical fibers operating near ∼6 μm.     

Structure and Properties of Silver Borate Glasses

Clear glasses form in the system Ag₂O-B₂O₃ up to about 35 mol% (65 wt%) Ag₂O. Infrared absorption, thermal expansion, and density data indicated an analogy to the Na₂O-B₂O₃ system. Pentaborate-triborate group pairs appear to be formed on addition of Ag₂O to B₂O₃ up to 20 mol% Ag₂O and diborate groups from 20 to 33 mol% Ag₂O. This interpretation is supported by the comparison of the infrared absorption spectra of quenched and crystallized glasses. One crystallization product, Ag₂O-4B₂O₃, was identified previously. A new compound starts to appear at 28 mol% Ag₂O. The theory that silver is generally present as a network modifier like sodium was substantiated by the comparison of the molar volume of sodium and silver borate glasses. Above 27 mol% Ag₂O some atomic silver is assumed to be present; below 15 mol%, exploratory studies indicate a two-phase structure within an immiscibility gap. A low-temperature internal friction peak in the glasses up to 28 mol% Ag₂O corresponds to the alkali peak in other glasses; a high temperature peak appearing in the 34 mol% Ag₂O glass is associated with the appearance of nonbridging oxygen in the system.     

Structure and Physicochemical Properties of Glasses in the Li2S–LiPO3 System

The temperature–concentration dependence of the electrical conductivity of glasses in the Li₂O–LiPO₃ and Li₂S–LiPO₃ systems is investigated. With the use of the Tubandt method, it is demonstrated that the electric current in glasses of these systems is provided by migration of lithium ions. The concentration dependence of the electrical conductivity is interpreted using the obtained data on the IR absorption spectra, density, microhardness, ultrasonic velocity, etc. It is found that the electrical conductivity of glasses in the Li₂S–LiPO₃ system is more than 10³ times higher than that in pure LiPO₃. The observed increase in the electrical conductivity is explained by the formation of sulfur-containing polar structural–chemical groupings of the Li⁺[S^–PO_3/2] type, whose dissociation energy is lower than that of similar oxide polar structural fragments. This results in an increase in the number of lithium ions involved in the electricity transport due to an increase in the degree of dissociation of polar structural–chemical units.     

Properties and Structure of Glasses in the System PbO-GeO2

Glasses are readily made from compositions containing up to 45 mol% PbO. The deviation of molar volume from ideality plotted vs composition shows a broad minimum at 70 to 80 mol% GeO₂, similar to the behavior of the alkali-GeO₂ glasses, indicating that the change in coordination of the Ge⁴⁺ ion from 4- to 6-fold occurs in this system, although maxima are not seen in plots of density and refractive index vs composition (mol%). Light scattering and electron microscopy indicate microstructure in glasses in the composition range 10 to 30 mol% PbO. This microstructure appears to affect the dc resistivity and viscosity but not the thermal-expansion coefficients.     

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.     

Physical Properties and Structure of Silica-Alumina-Europium Oxide Glasses

SiO₂–Al₂O3–Eu₂O₃ glasses were prepared for the composition 50siO₂·(50 – x )Al₂O_3·xEu₂O₃, and their density, sound velocity, and elastic modulus were measured. The chemical shift of the AIK a band emission spectra and the isomer shift of ¹⁵¹Eu by Mössbauer effect were obtained to determine the coordination states of Al³⁺ and Eu³⁺ ions in these glasses. It was found that the coordination number of Eu³⁺ ions was 12 and that the average coordination number of A1³⁺ ions was almost 5 in these glasses. By introducing Eu₂O₃, the packing of constituent ions was strongly enhanced and the elastic modulus increased in this system. The compositional dependence of the molar volume and elastic modulus were explained by these states of high coordination number for Eu³⁺ and low coordination number for Al³⁺ ions compared with those in the corresponding M₂O₃ crystals.     

Electrical Properties and the Structure of Glasses in the Li2SO4–LiPO3 System

Electrical characteristics, namely, the temperature–concentration dependence of the electrical conductivity and the concentration dependence of the transport numbers of lithium ions (determined with the use of the Tubandt method) are investigated for glasses in the Li₂SO₄–LiPO₃ system. It is revealed that only lithium ions are involved in charge transfer. The IR absorption spectra, density, microhardness, and ultrasonic velocity are measured. An analysis of the experimental results obtained demonstrates that SO^2- ₄ ions form terminal groups and can be incorporated into polyphosphate structural fragments. An increase in the electrical conductivity and a decrease in the activation energy for electrical conduction are interpreted in the framework of a crossover of the migration mechanism. In lithium metaphosphate, lithium ions predominantly migrate through the interstitial mechanism. However, an increase in the lithium sulfate content in the initial glass leads to an increase in the fraction of charge carriers that migrate according to the vacancy mechanism.     

Structure and Nonlinear Optical Properties of Lanthanide Borate Glasses

The third–order nonlinear optical susceptibility, χ⁽³⁾, of lanthanide (lanthanum, praseodymium, neodymium, and samarium) borate glasses has been measured by the third harmonic generation method. The structure of the present glass system has been studied by infrared and Raman spectroscopic methods. The network structures of the present Ln₂O₃–B₂O₃ glasses have been confirmed to be basically similar to each other. Praseodymium, neodymium, and samarium borate glasses exhibit χ⁽³⁾ values that are larger than lanthanum borate glasses, because of the optical resonance effect, in accordance with the f – f transition. Especially, the χ⁽³⁾ value for 30Pr₂O₃·70B₂O₃ glass is 1.8 × 10⁻¹² esu, which is a factor of ∼60 larger than that of SiO₂ glass. This striking enhancement of χ⁽³⁾ is mainly attributed to the large transition moment to the first excitation state.     

An Overview of the Structure and Properties of Silicon-Based Oxynitride Glasses

The silicon oxynitride glasses take advantage of nitrogen bonding to attain high elastic modulus, increased softening temperatures and viscosities, greater slow crack growth resistance, and modest gains in fracture resistance. Of the oxynitride glasses, the Si–Y–Al-based oxynitride glasses have been most extensively studied and a degree of success has been achieved in understanding how changes in glass composition affect structural parameters and their relationship with properties. More recent studies have focused on the Si–RE–Me oxynitride glasses, where Me is primarily Al or Mg and rare earth (RE) includes most of the lanthanide series elements. These glasses possess a range of elastic, thermal, mechanical, and optical properties, which can be correlated with the strength of the RE bond in terms of the cationic field strength. However, such correlations require knowledge of not only the RE valence state but also its coordination with the anions. Herein, the current state-of-the-art understanding of the properties and structural parameters of oxynitride glasses and their interrelationships are reviewed.     

Spectroscopic Analysis of the Structure and Properties of Alkali Tellurite Glasses

Structural development of tellurite glasses with the addition of Li₂O and Na₂O has been studied using infrared, Raman, and X-ray photoelectron spectroscopies. The increase in intensity of the peak at 755 cm⁻¹ in the infrared spectra as compared to the peak at 620 cm ⁻¹ suggests the transformation of TeO₄ building units to TeO₃ pyramids with the addition of alkali oxide. Proposed structural change is further supported by the strong compositional dependence of the 755-cm⁻¹ peak in the Raman spectra as well as by the formation of a shoulder in the O 1 s peak of X-ray photoelectron spectra. In contrast to alkali silicate glasses, formation of nonbridging oxygens with the addition of alkali oxide is not observed.     

Properties and Structure of Lithium Borate and Strontium Borate Glasses

Experimental results for some physical properties of Li₂O-B₂O₃ and SrO-B₂O₃ glasses with high modifier content showed anomalies in the composition dependence of many properties such as thermal expansion coefficient, transformation temperature, softening temperature, density, and refractive index at 30 to 33 mol% modifier oxide in these glasses. These anomalies are attributed to the formation of nonbridging oxygens near this composition.     

Physical Properties and Structure of Silicate Glasses: I, Additive Relations in Alkali Binary Glasses

Correlations between certain physical properties, P , and all eighteen compositional ratios between the five ionic parameters of the system were studied with a computer for the five alkali silicates. Linear relations were found between P and the alkali/silica, alkali/oxygen, and silica/alkali ratios for certain regions of the glass field when the P's are expressed in proper molar terms. Specific volume and heat of formation data indicate three linear regions with two sharp break points between. The log electrical resistivity and the volatilization loss show two such regions and only the second break point. The break points, while structural in origin, must therefore occur for different reasons. The break points are the same for all P's and coincide with the eutectics. The constants of the linear relations are the partial molar quantities associated with P. Break points are not found in the molar refractivity data, so that no change in ligancy for these systems is indicated.     

Structure and Physical Properties of Borosilicate as Potential Bioactive Glasses

Borosilicate bioactive glasses containing titanium dioxide were prepared and investigated. The corrosion behavior of samples was examined for all samples upon immersion in phosphate solution. The erosion of the outer surface and ion exchange processes of the glass with the surrounding solution were studied by measuring the weight loss. Results were compared with samples that do not contain titanium dioxide. The final result of the reaction is the precipitation of hydroxyapatite. Characterization of the glasses was carried out by FTIR (Fourier transform infrared) absorption spectra before and after immersion in phosphate solution. The different crystalline phases and crystallographic parameters were explored using X-ray diffraction (XRD) analyzes and all indicate the precipitation of hydroxyapatite. A scanning electron microscope (SEM) is used to observe the morphological changes of the surfaces upon immersion. The atomic ratio of the final result product was obtained by the energy dispersive x-ray analysis (EDX) unit attached to the SEM. Changes in pH of the leaching solution were measured and evaluated. All measurements confirm that the studied glass has a high degree of biological activity which makes it very suitable for the field of biomaterials and other various medical applications.