Short range order and glass transition in AgIAg2OB2O3 vitreous electrolytes

Several experimental techniques are used to study the short range order, the dynamics and the glass transition in AgIAg₂B₂O₃ compounds. Addition of Ag₂O to B₂O₃, up to [Ag₂O]/[B₂O₃] ?0.5 modifies the borate network by creating a BO₄ unit for each silver added. Addition of AgI decreases the glass transition temperature (T_g) but has only minor effects on the short range structure of the borate network. Silver iodide is partially accomodated in the interstices of the glass network. The relationship among a tentative structural picture, the ion transport phenomena and the low temperature dynamics are discussed.An investigation of the dynamics in the AgI·Ag₂O·2B₂O₃ glass near and above T_g is presented. With NMR techniques, we monitor the onset of tumbling of the borate units and the dynamical effects of crystallization and/or aging of the glass. Hysteresis effects in the ionic conductivity (σ) temperature dependence and the non-Arrhenian behavior of σT near T_g are interpreted in terms of structural modifications occurring at elevated temperatures in the glass.     

Thermal and electrical properties of BaO-B2O3-ZnO glasses

Glasses in the BaO-ZnO-B₂O₃ system were examined as potential replacement for PbO glass frits with low firing temperature (500-600 °C) for the dielectric layer of a plasma display panel (PDP). The glasses were evaluated for glass transition temperature (T_g), thermal expansion coefficient (α) and dielectric constant ε. The electrical and the thermal properties were also compared with theoretical data calculated by a known empirical equation. T_g of the glasses varied between 480 and 560 °C, and α was in the range of 7-9×10⁻⁶ K⁻¹. The dielectric constant ranges from 14 to 19 and the theoretical data showed lower α and ε than the experimental data. The results suggest that BaO-ZnO-B₂O₃ glasses would be suitable as an alternative to Pb-based dielectric layer in PDPs.     

Thermal and some physical properties of glasses in the La2O3−CaO−B2O3 ternary system

Glasses in the La₂O₃−CaO−B₂O₃ ternary system were studied. The glass forming range as determined by the appearance of the annealed cast was found to match previously published findings. Clear glasses were formed in the composition range of 5.7−19.1 mol% La₂O₃ with constant B₂O₃ content of 71.4 mol%, and in glasses of constant La₂O₃:CaO ratio of 1:4 with B₂O₃ content in the range of 71.4-55.0 mol%. The non-linear optical crystalline phase La₂Ca₂B₁₀O₁₉ was crystallized from the clear glasses after heat treatments, as determined by powder XRD. Two types of the LaBO₃ crystalline phases were detected in the partially and the fully crystallized glass compositions outside the glass forming range. Data are reported for the glass transition temperature (T_g), dilatometric softening point (T_d), linear coefficient of expansion (α), onset crystallization temperature (T_x), exothermal peak temperature (T_P), density (ρ) and index of refraction (n_D) in the clear glasses.     

Thermo-optic properties of B2O3 doped Li2O-Al2O3-SiO2 glass-ceramics

Reduction in the temperature coefficient of the optical path length, dS/dT of Li₂O-Al₂O₃-SiO₂ glass-ceramics with near-zero thermal expansion coefficient was attempted using control of the temperature coefficient of electronic polarizability, ?, and the thermal expansion coefficient, α. The dS/dT value of 2.6 mol% B₂O₃-doped glass-ceramic was 12.5  × 10⁻⁶/°C, which was 0.9 ×  10⁻⁶/°C smaller than that of B₂O₃-free glass-ceramic. On the other hand, reduction in dS/dT through B₂O₃ doping was not confirmed in precursor glasses. Results showed that reduction in dS/dT of the glass-ceramic through B₂O₃ doping is caused by the reduction in ?. The reduction in ? from B₂O₃ doping was probably attributable to numerical reduction in non-bridging oxide ions with larger ? value by the concentration of boron ions in the residual glass phase. In addition, application of hydrostatic pressure during crystallization was effective to inhibit precipitation of β-spodumene solid solution, which thereby decreases dS/dT. The dS/dT value of B₂O₃-doped glass-ceramic crystallized under 196 MPa was 11.7 ×  10⁻⁶/°C. That value was slightly larger than that of silica glass. The α value of this glass-ceramic was smaller than that of silica glass.     

On the local coordination of Fe in Fe2O3-glass and Fe2O3-glass ceramic systems containing Pb, Na and Si

The effect of the composition and casting temperature on the structural role of Fe in a series of binary (Fe₂O₃-PbO and Fe₂O₃-Na₂O) and ternary (Fe₂O₃-PbO-SiO₂) glass and glass ceramic materials is studied by means of X-ray fluorescence (XRF) mapping, X-ray absorption fine structure (XAFS) and Mössbauer spectroscopies. According to the Mössbauer results the majority of Fe exists in the Fe⁺³ state. The XRF maps reveal that Fe-rich islands evolve into the vitreous matrix of ternary samples that contain more than 40 wt% Fe₂O₃. In these samples the XAFS results disclose that 40-43 at.% of the Fe atoms belong to the Fe-rich microcrystalline islands formed by Fe_xO_y oxides. Furthermore, the structural role of Fe⁺³ in the ternary glasses is found to depend on the Fe₂O₃ content. Finally in the binary Fe₂O₃-PbO systems the majority of Fe⁺³ is octahedrally coordinated in the Fe₂O₃ and/or PbFe₁₂O₁₉ crystalline phases.     

Fabrication and properties of novel low-melting glasses in the ternary system ZnO-Sb2O3-P2O5

Glasses in the ternary system ZnO-Sb₂O₃-P₂O₅ were investigated as potential alternatives to lead based glasses for low temperature applications. The glass-forming region of ZnO-Sb₂O₃-P₂O₅ system has been determined. Structure and properties of the glasses with the composition (60 − x)ZnO-xSb₂O₃-40P₂O₅ were characterized by infrared spectra (IR), differential thermal analysis (DTA) and X-ray diffraction (XRD). The results of IR indicated the role of Sb³⁺ as participant in glass network structure, which was supported by the monotonic and remarkable increase of density (ρ) and molar volume (V_M) with increasing Sb₂O₃ content. Glass transition temperature (T_g) and thermal stability decreased, and coefficient of thermal expansion (α) increased with the substitution of Sb₂O₃ for ZnO in the range of 0-50 mol%. XRD pattern of the heat treated glass containing 30 mol% Sb₂O₃ indicated that the structure of antimony-phosphate becomes dominant. The improved water durability of these glasses is consistent with the replacement of easily hydrated phosphate chains by corrosion resistant P-O-Sb bonds. The glasses containing ?30 mol% Sb₂O₃ possess lower T_g (<400 °C) and better water durability, which could be alternatives to lead based glasses for practical applications with further composition improvement.     

Thermodynamical miscibility in 0.8[xB2O3-(1 − x)P2O5]-0.2K2O glasses

The thermodynamical miscibility in 0.8[xB₂O₃-(1 − x)P₂O₅]-0.2K₂O glasses has been studied by measuring the glass transition temperature and the mixing enthalpy. Measurements have been performed by differential scanning calorimeter and hydrofluoric acid solution calorimetry at 298 K. The enthalpies of mixing are significantly negative over the whole range of composition. The results are discussed in terms of intermolecular associations.     

Effects of Nb2O5 Replacement by Er2O3 on elastic and structural properties of 75TeO2-(10 − x)Nb2O5-15ZnO-(x)Er2O3 glass

Tellurite 75TeO₂-(10 − x)Nb₂O₅-15ZnO-(x)Er₂O₃; (x = 0.0-2.5 mol%) glass system with concurrent reduction of Nb₂O₅ and Er₂O₃ addition have been prepared by melt-quenching method. Elastic properties together with structural properties of the glasses were investigated by measuring both longitudinal and shear velocities using the pulse-echo-overlap technique at 5 MHz and Fourier Transform Infrared (FTIR) spectroscopy, respectively. Shear velocity, shear modulus, Young's modulus and Debye temperature were observed to initially decrease at x = 0.5 mol% but remained constant between x = 1.0 mol% to x = 2.0 mol%, before increasing back with Er₂O₃ addition at x = 2.5 mol%. The initial drop in shear velocity and related elastic moduli observed at x = 0.5 mol% were suggested to be due to weakening of glass network rigidity as a result of increase in non-bridging oxygen (NBO) ions as a consequence of Nb₂O₅ reduction. The near constant values of shear velocity, elastic moduli, Debye temperature, hardness and Poisson's ratio between x = 0.5 mol% to x = 2.0 mol% were suggested to be due to competition between bridging oxygen (BO) and NBO ions in the glass network as Er₂O₃ gradually compensated for Nb₂O₅. Further addition of Er₂O₃ (x > 2.0 mol%) seems to further reduce NBO leading to improved rigidity of the glass network causing a large increase of ultrasonic velocity (v_L and v_S) and related elastic moduli at x = 2.5 mol%. FTIR analysis on NbO₆ octahedral, TeO₄ trigonal bipyramid (tbp) and TeO₃ trigonal pyramid (tp) absorption peaks confirmed the initial formation of NBO ions at x = 0.5 mol% followed by NBO/BO competition at x = 0.5-2.0 mol%. Appearance of ZnO₄ tetrahedra and increase in intensity of TeO₄ tbp absorption peaks at x = 2.0 mol% and x = 2.5 mol% indicate increase in formation of BO.     

Structural investigations of copper doped B2O3-Bi2O3 glasses with high bismuth oxide content

Raman and infrared spectroscopy have been employed to investigate the 99.5%[xB₂O₃(1−x)Bi₂O₃]0.5%CuO glasses with different Bi/B nominal ratios (0.07?x?0.625) in order to obtain information about the competitive role of B₂O₃ and Bi₂O₃ in the formation of the glass network. The glass samples have been prepared by melting at 1100 °C and rapidly cooling at room temperature. In order to relax the structure, to improve the local order and to develop crystalline phases the glass samples were kept at 575 °C for 10 h. The influence of both Bi₂O₃ and CuO on the vitreous B₂O₃ network as well as the local order changes around bismuth and boron atoms in as prepared and heat treated samples was studied. Structural modifications occurring in heat treated samples compared to the untreated glasses have been observed.     

Magnetic behaviour of 20Fe2O380[3B2O3(1−χ)PbOχAs2O3] glasses

The results of magnetic measurements performed on 20Fe₂O₃80[3B₂O₃(1?χ)PbOχAs₂O₃] glasses, in the temperature range 4.2 to 300 K are reported. By decreasing the temperature a downward curvature of reciprocal susceptibility is observed for T<50 K. The composition dependence of the paramagnetic Curie temperatures and Curie constants is discussed.     

Synthesis and physical properties of glasses in the Sb2O3-PbCl2-MoO3 system

Lead chloroantimonite glasses form stable binary glasses that may accommodate numerous oxides or halides as a third component. Molybdenum trioxide is a glass progenitor leading to molybdate glasses. Ternary glasses have been synthesized and studied in the Sb₂O₃-PbCl₂-MoO₃ system. Compositional limits of glass formation are reported and two series of glass samples have been prepared corresponding to the general formulas: (90 − x)Sb₂O₃-xPbCl₂-10MoO₃ and (90 − x)Sb₂O₃-xMoO₃-10PbCl₂. Glass transition temperature is close to 290 °C at high Sb₂O₃ content and decreases as antimony oxide is substituted by MoO₃ or PbCl₂. Position, width and intensity of crystallization peak suggest that devitrification rate is small in some composition ranges. The evolution of density, thermal expansion, refractive index and microhardness has been studied as a function of composition parameter x. Deviations from linearity are observed. They suggest structural changes in the case of the MoO₃/Sb₂O₃ substitution while it appears that molar volume increases linearly versus lead content in the other series of glasses. Refractive index is close to 2.04. Optical transmission ranges from 550 nm in the visible spectrum to 5.5 μm in the infrared. It is limited by extrinsic absorption bands arising from hydroxyls and silicon impurities. Young's, bulk and shear moduli have been measured for the two series of samples.     

Influence of Y2O3 on structural and optical properties of SiO2-BaO-ZnO-xB2O3-(10−x) Y2O3 glasses and glass ceramics

SiO₂-BaO-ZnO-xB₂O₃-(10−x) Y₂O₃, (0 ≤ x ≤ 10) glasses are synthesized. The effect of Y₂O₃ on the structural and optical properties of glasses has been investigated using different characterization techniques. The results are discussed in light of non-bridging oxygens (NBO), optical basicity and heat-treatment of glasses. The band gap has been calculated for as cast and heat-treated glasses. The band gap energy is found to decrease with the increasing content of Y₂O₃ in the glasses and heat-treatment. The presence of the crystalline phase in the glass matrix showed remarkable effect on band gap which decreases to semiconducting range.     

Glass formation in the Sb2O3-CdCl2-SrCl2 ternary system

Vitreous systems based on antimony oxide Sb₂O₃ have been investigated. The limits for glass formation are reported in the Sb₂O₃-CdCl₂-SrCl₂ ternary system, and in the Sb₂O₃-SrCl₂-(0.5CdCl₂ + 0.5ZnCl₂) pseudo ternary system. Amorphous state is confirmed by XRD patterns. Thermal measurements implemented by differential scanning calorimetry show that Tg is above 300 °C. As a general trend, Tg increases with chloride content. These glasses have an extended transmission in the mid-infrared spectrum with a refractive index larger than 2. The influence of the CdCl₂/Sb₂O₃ substitution on the physical properties has been studied in the (90 − x)Sb₂O₃-xCdCl₂-10SrCl₂ system: thermal expansion, Vickers microhardness, Young and bulk modulus decrease as cadmium concentration increases. An inverse dependence is observed for shear modulus. This behaviour is discussed in relation to structural hypothesis.     

Thermal expansion of glasses in the As2Se3–AsI3 system

Thermal expansion coefficients (α) of glasses in the As₂Se₃–AsI₃ system are measured in the glass transition region and temperature dependence of the fictive temperature is calculated on the basis of relaxation model. It is found that the increase of AsI₃ content results in: an increase of α, decrease of the glass transition temperature (T_g), increase of the α change at T_g, an effect of quenching rate on α, and also changes in the structural relaxation times spectrum. The data are discussed within the framework of the assumption that the addition of AsI₃ to As₂Se₃ results in: (1) destruction of the As₂Se₃ glass network, (2) structural inhomogeneity of the glasses increase, (3) the temperature dependence of chemical–structural equilibria occurring in the liquid state increases.     

Viscosity of (GeSe2)x(Sb2Se3)1−x undercooled melts

Viscosity of (GeSe₂)_x(Sb₂Se₃)_1−x undercooled melts (x = 0.4-0.8) was measured using parallel-plate method and penetration method. By using these two techniques viscosity of the whole measurable region of undercooled melt and of the part of glass region can be measured. In this relatively broad viscosity interval (seven orders of magnitude) all measured samples show Newtonian behavior and the dependence of their viscosity on temperature can be described by a simple Arrhenius equation. The kinetic fragilities calculated from these dependencies show similar compositional dependence as heat capacity changes at glass transition measured by DSC.     

Quenched glasses in the systems of Li2O with Al2O3, Ga2O3 and Bi2O3

By rapid quenching in a twin roller apparatus, glass was found to occur widely in the systems of Li₂O with Al₂O₃, Ga₂O₃, Bi₂O₃ and in mixed systems. Examination of the resulting flakes by X-ray powder diffraction, differential thermal analysis, and capacitance data revealed the occurrence of glass, glass transitions, crystallization exotherms and the nature of some of the crystallization paths.The log ionic conductivity of the glasses was found to follow a linear relationship with the Li concentration. Evidence was observed for three new metastable crystalline phases, one in the Li₂OAl₂O₃ system and two in the Li₂OBi₂O₃ system. The latter system also showed evidence for the occurrence of two glasses at almost all compositions.     

Phase separation and crystallization in the system SiO2-Al2O3-P2O5-B2O3-Na2O glasses

The phase separation and crystallization behavior in the system (80 − X)SiO₂ · X(Al₂O₃ + P₂O₅) · 5B₂O₃ · 15Na₂O (mol%) glasses was investigated. Glasses with X = 20 and 30 phase separated into two phases, one of which is rich in Al₂O₃-P₂O₅-SiO₂ and forms a continuous phase. Glasses containing a larger amount of Al₂O₃-P₂O₅ (X = 40 and 50) readily crystallize and precipitates tridymite type AlPO₄ crystals. It is estimated that the phase separation occurs forming continuous Al₂O₃-P₂O₅-SiO₂ phase at first, and then tridymite type AlPO₄ crystals precipitate and grow in this phase. Highly transparent glass-ceramics comparable to glass can be successfully obtained by controlling heat treatment precisely. The crystal size and percent crystallinity of these transparent glass-ceramics are 20-30 nm and about 50%, respectively.     

Influence of Nd2O3 on the thermal and dielectric properties of Pb-based lead borosilicate glasses

Neodymium has been employed in various Pb-based glass compositions containing ZnO, MgO, CaO, and BaO, to obtain low melting glasses for use as dielectric materials. Thermal analysis (DTA, TMA) was applied for both qualitative and quantitative thermal properties (T_g, CTE) of the glasses, and impedance analysis of the dielectric properties (ε_r, tanδ) was performed. It was found that with increasing Nd₂O₃, the glass transition temperature (T_g), the dilatometer softening point (T_d) and dielectric constant (ε_r) became higher. Also, a peak shift suggesting neodymium oxide introduced structural changes was found with IR spectra and XPS. These seem to support the conclusion that the addition of increased amounts of Nd₂O₃ can lead to a more rigid glass structure.     

Spectroscopic properties of Er-doped Na2O-Sb2O3-B2O3-SiO2 glasses

Spectroscopic properties of Er³⁺-doped Na₂O-Sb₂O₃-B₂O₃-SiO₂ glasses have been investigated for developing 1.5-μm broadband fiber amplifiers. An intense 1.5-μm near infrared emission with a broad full width at half maximum (FWHM) of 88 nm has been obtained for Er³⁺-doped 5Na₂O-20Sb₂O₃-35B₂O₃-40SiO₂ glass upon excitation with a 980 nm laser diode. The obtained emission cross-section of the ⁴I_13/2 → ⁴I_15/2 transition and the lifetime of the ⁴I_13/2 level of Er³⁺ ions are 6.8 × 10⁻²¹ cm² and 0.36 ms, respectively. It is noted that the product of the emission cross-section and the FWHM of the glass, σ_e × FWHM, is as great as 598.4 × 10⁻²¹ cm² nm, which is comparable or higher than that of Er³⁺-doped bismuth-based and tellurite-based glasses. These special optical properties encourage in identifying them as important materials for potential applications in high performance optics and optical communication networks.     

Thermal, chemical, optical properties and structure of Er-doped and Er/Yb-codoped P2O5-Al2O3-ZnO glasses

This study was explored in series of the optical, thermal, and structure properties based on 60P₂O₅-10Al₂O₃-30ZnO (PAZ) glasses system that doped with varied rare-earth (RE) elements Yb₂O₃/Er₂O₃. The glass transition temperature, softening temperature and chemical durability were increased with RE-doping concentrations increasing, whereas thermal expansion coefficient was decreased. In the optical properties, the absorption and emission intensities also increase with RE-doping concentrations increasing, When Er₂O₃ and Yb₂O₃ concentrations are over than 3 mol% in the Er³⁺-doped PAZ system and Yb³⁺-doped concentration is over than 3 mol% for Er³⁺/Yb³⁺-codoped PAZ system, the emission intensity significantly decreases presumably due to concentration quenching, formation of the ions clustering, and OH⁻ groups in the glasses network. It is suggested that the maximum emission cross-section (σ_e) is 7.64 × 10^− 21 cm² at 1535 nm is observed for 3 mol% Er³⁺-doped PAZ glasses. Moreover, the maximum σ_e × full-width-at-half-maximum is 327.8 for 5 mol% Er³⁺-doped PAZ glasses.