Intrinsic and impurity infrared absorption in As2Se3 glass

A quantitative study of infrared absorption in the 250–4000 cm^?1 region of As₂Se₃ glasses doped with small amounts of As₂O₃ or purified by various procedures has been carried out with particular attention to absorption in the wavelength regions of the CO₂ and CO lasers. The dependence of the relative intensities of the oxide impurity bands in the 650–1340 cm^?1 region on the total amount of As₂O₃ added to the glass indicates the existence of three distinct oxide-impurity species. A number of higher-frequency impurity bands which are due to the presence of hydrogen in the glass and whose intensities are highly dependent on the glass-melting conditions have been observed and classified. Intrinsic multiphonon absorption in the 400–1100 cm^?1 region has been interpreted in terms of combination and overtone bands of the two highest-frequency fundamental vibrational modes. Absorption coefficients of As₂Se₃ glass in the 920–1090 cm^?1 CO₂ laser region are limited by intrinsic multiphonon absorption to values of around 10^?2 cm^?1. The lowest absorption coefficients measured in the 1700–2000 cm^?1 CO laser region were around 2 × 10^?3 cm^?1 and may contain contributions from hydrogen-impurity bands.     

Bulk and impurity infrared absorption in 0.5 As2Se30.5 GeSe2 glass

A study of infrared absorption in the 250–4000 cm^?1 region has been carried out for 0.5 As₂Se₃0.5 GeSe₂ glasses quantitatively doped with oxide impurity. The frequencies of the intrinsic 2- and 3-phonon absorption bands at 490 and 690 cm^?1 correspond well to those predicted from combinations of the high frequency bands in the first order IR and Raman spectra of As₂Se₃ and GeSe₂ glasses.Glasses doped with As₂O₃ exhibit the same oxide impurity absorptionbands as those doped with GeO₂. Unlike As₂Se₃ glass, at impurity concentrations up to 1000 ppm As₂O₃, 0.5 As₂Se₃0.5 GeSe₂ glass exhibits only one major oxide impurity species, characterized by absorption bands at 780 and 1260 cm^?1 and due to oxygen bonded to network Ge. The observation of a much weaker network AsO vibration band at 670 cm^?1 confirms that oxygen bonds preferentially to Ge in this glass. The same minor oxide species appears to determine excess IR absorption at the CO₂ laser wavelength of 10.6 μm in both As₂Se₃ and 0.5 As₂Se₃ 0.5 GeSe₂ glasses. The frequencies and intensities of absorption bands due to hydrogen impurities are also quite comparable for these two materials.     

Peculiar temperature-dependent fluorescence of EuCl3 in LiCl molten salt as a result of phase changes

Fluorescence spectra were obtained in situ as a function of temperature (ranging from room temperature to 956 K) from a melt of EuCl₃ and LiCl. Three different characteristic Eu²⁺ fluorescence bands, associated with phase changes, were observed. The critical fluorescence dependence on temperature appearing in the blue fluorescence were resulted from the radiative relaxation from 4f⁶5d¹ excited state to 4f⁷ (⁸S_7/2) ground state of Eu²⁺, which was reduced from Eu³⁺ of EuCl₃ at high temperature. The fluorescence studies could provide information regarding the phase changes estimated as the stable dihalide, aggregation, and precipitation states of Eu²⁺ in alkali halide not only crystallic but also fluidic melting matrix.     

An EXAFS study of Ag3AsS3 glass

The local structures of Ag₃AsS₃ glass at 80 and 300 K have been investigated by extended X-ray absorption fine structure analysis. By comparing the glass structure with that of Ag₃AsS₃ crystal (proustite), the possibility of ionic conduction by this glass is discussed. The local structure around an As atom in the glass is similar to that in the crystal. This fact suggest that, even in the glass structure, the As atoms from AsS₃ trigonal pyramids of shape similar to that in the crystal. The Ag---S distance (2.449 Å at 300 K) and the large root mean square displacement, σ, for the Ag---S atomic pairs in the glass, groups with a by the parameter fitting method, show that the Ag atoms are quite randomly distributed around the AsS₃ groups with a similar Ag---S distance to that in the crystal. Further, it is possible that the large thermal contribution to σ_Ag---S² for the glass may indicate the involvement of the Ag atoms in ionic conduction.     

Structure analysis of MgSiO3 glass

The structure of MgSiO₃ glass was investigated by a combination of radial distribution function (RDF) analysis with an intensity comparison method on the basis of X-ray diffraction data. There appeared five peaks at 1.63, 2.08, 2.58, 3.25 and 4.2 Å in the RDF curve. The short range structure was found to be similar to that observed in pyroxenes: single chains composed of SiO₄ tetrahedra are linked by Mg²⁺ ions laterally. The Mg²⁺ ion is surrounded by six oxygen atoms on average, four of which form MgO pairs with an average distance of 2.08 Å and the remainder Mg O pairs of 2.5 Å which contribute to the formation of the third peak at 2.58 Å in the RDF curve together with the OO pairs (2.66 Å) in SiO₄ tetrahedra. The calculated intensity curve based on this model was in good agreement with the observed one.     

A coherent quasielastic neutron scattering study of NO3 ion motion in molten RbNO3

Quasielastic neutron scattering experiments have been performed on molten RbNO₃, The quasielastic spectra are composed of narrow and broad coherent components. The narrow component is assigned to the translational motion due to the diffusion of the center of gravity of each ion. The broad component corresponds to fast intra-ionic motions within the nitrate ion. From the momentum dependence of the broad component, it is concluded that the nitrate ion in molten RbNO₃ is mainly subjected to a rotational vibration centered around the C₃ axis and that the form of the nitrate motion around C₃ axis does not change with increasing temperature.     

Vibrational properties of As2S3 glass

Vibrational densities of states and infrared and Raman spectra have been calculated for a structural model of As₂S₃ glass. The calculations are based on simple semi-empirical forms for interatomic potentials, electric dipole moment and Raman polarizability. The bands of the calculated spectra agree well with those of the observed infrared and Raman spectra of As₂S₃ glass in intensity and position, although a small concentration of the wrong SS bonds remains in the structural model and causes an additional peak in the higher frequency region. The calculated depolarization ratio of the Raman spectra is consistent with the observed one.     

Effect of additives in the salt bath on glass strengthening

In this paper, we mainly study the effects of anion or anion group additives (such as the monovalent anions OH⁻, Cl⁻ or NO₃⁻, the divalent anion SO₄⁻, and the trivalent anion PO₄³⁻, respectively) in a salt bath of KNO₃ on glass strengthening. The Na₂O---Al₂O₃---SiO₂ system is selected to be the base glass.     

The preparation and electrical switching properties of nickel sulphides in As2S3 glass

A preliminary investigation into the formation of ‘glasses’ from mixtures of arsenic and nickel sulphides is reported. Memory- and threshold-switching devices have been produced from glasses containing particles of nickel sulphide. Threshold switches show a high resistance in the off-state ($\text{> 10}{}^6\text{μ}$), and a linear on-state.     

Effect of Si3N4 on chemical durability of chalcogenide glass

Chemical durability of the Si₃N₄ doped (up to 0.5 wt%) chalconitride glasses was evaluated by weight losses of glass samples after immersion in deionized water, H₂SO₄, HCl and NaOH solutions. IR spectra and SEM were used as an aid to examine the surface structure of corroded glass samples. Weight loss measurements showed a poorer stability of non-oxide glasses in basic solution than in acid solution, and the Si₃N₄ doping was found to improve chemical durability. Comparison of IR spectra of samples exposed to the basic solution with their original ones suggested the higher content of OH⁻ in its reaction layers, indicating that the corrosion of the present non-oxide glasses in the basic solution may result from the breakdown of the bridging Se due to an attack launched by OH⁻. The SEM evidence confirmed that Si₃N₄ doping did hinder the OH⁻ attacks on Ge and/or As, which is most likely related to incorporation of the three-coordinated N into the glass network, as supported by a comparison of the IR transmitting spectrum between uncorroded chalconitride glass and undoped chalcogenide glass.     

Laser precipitation of SnO2 nanocrystals in glass and energy transferred-fluorescence of Eu ions

SnO₂ nanoparticles having an average particle size of 5 nm were precipitated in a transparent glass by irradiation with an 800 nm femtosecond laser. Glass was prepared to co-dope Sn⁴⁺ and Eu³⁺ ions by a sol–gel method, followed by heating in H₂ gas atmosphere to form the Sn⁰₂ point defects with a molecular-like electronic structure in the twofold-coordinated Sn atoms. Upon laser irradiation, the Sn⁰₂ defects react with oxygen, forming SnO₂ nanocrystals. When excited at the energy corresponding to the absorption edge of the SnO₂ nanocrystals, the energies, which are absorbed by the quantum-dot effect in the nanosized crystals, are efficiently transferred to the Eu³⁺ ions, resulting in the large enhanced fluorescence intensities from the Eu³⁺ ions. The observed phenomenon suggests application to high-density memory devices.     

Crystallization behavior of (GeS2)0.1(Sb2S3)0.9 glass

The crystal growth kinetics of antimony trisulfide in (GeS₂)_0.1(Sb₂S₃)_0.9 glass has been studied by microscopy and DSC. The linear crystal growth kinetics has been confirmed in the temperature range 492 ? T ? 515 K (E_G = 405 ± 7 kJ mol⁻¹). The applicability of standard growth models has been assessed. From the crystal growth rate corrected for viscosity plotted as a function of undercooling it has been found that the most probable mechanism is interface controlled 2D nucleated growth. The non-isothermal DSC data, corresponding to the bulk sample, can be described by the Johnson-Mehl-Avrami equation.     

Structural study of (As2S3)0.6(GeS2)0.4 glass

(As₂S₃)_0.6(GeS₂)_0.4 glass in non-irradiated and γ-irradiated states has been studied by using high-energy synchrotron X-ray diffraction, extended X-ray absorption fine structure spectroscopy, and positron annihilation lifetime spectroscopy. The experimental results are explained by the local changes around As and Ge atoms upon irradiation. These changes are suggested to involve chemical bonds distortion, formation of defective bonds with wrong coordination, rotation of structural units and appearance of additional free volume in the glass network.     

Non-isothermal crystallization kinetics of ZnO-BaO-B2O3-SiO2 glass

Glass of composition 40SiO₂-30BaO-20ZnO-10B₂O₃ (mol%) was made by conventional melting and casting process. Crystallization kinetics of above glass has been investigated under non-isothermal conditions, using the formal theory of transformations for heterogeneous nucleation. The procedure is applied to the experimental data obtained by differential thermal analysis (DTA), using continuous-heating techniques. The crystallization results are analyzed, and both the activation energy of crystallization process as well as the crystallization mechanism is characterized. Dilatometric measurement of this glass was also done and data obtained was used to calculate the viscosity of the formed glass. Development of crystalline phases on thermal treatments of the glass at various temperatures has been analyzed by X-ray diffraction. Microstructure of the crystalline phases was investigated by scanning electron microscopy (SEM) and the development of various structural features with variation in heat treatment cycle was observed. The nucleation and growth of these phases in the matrix of glass has been described and discussed.     

The role of PbO on crystallization in PbO-SrO-TiO2-SiO2 glass

An investigation of the crystallization in the PbO-SrO-TiO₂-SiO₂ glass system demonstrates that the crystallization temperature of the glass decreases with an increase of the mole fraction of PbO. The second crystalline phase, SrTiO₃, was present when the mole fraction of PbO is more than 0.35, and impaired the piezoelectric coefficient of the glass ceramics in the main crystalline phase, Sr₂TiSi₂O₈.     

Electronic relaxation in the PbOSiO2Fe2O3 glass system

The a.c. and d.c. conductivities of PbOSiO₂ glass with 0–10 mole% Fe₂O₃ additions were measured in the temperature range 77–700 K. Two relaxation processes were noted. The relaxation mechanism at lower temperatures is due to polaron hopping between ferric-ferrous ion pairs with a distribution of relaxation times which is energy independent. The second relaxation phenomenon, at higher temperatures is polaron hopping along iron ion chains in the glass of which the pairs responsible for the first process are a part. A theoreticalmodel is proposed and additional evidence for this model is presented in the form of magnetic susceptibility and electron spin resonance (esr) data.     

The effect of minor additions of P2O5 on some phase transformations of plate glass

The effects of additions of several tenths of a per cent of P₂O₅ on the devitrification behavior of plate glass with the primary phase of tridymite are different from that with the primary phase of wollastonite. But they still follow the phase equilibrium relationship of multicomponents. By examinations with TEM, and measurements of electrical resistivities, it is indicated that phase separation of plate glass may be promoted with a minor addition of P₂O₅. Through XPS measurements it is further suggested that such an addition causes a certain change in the structure of the plate glass.     

Medium range order and optical properties of As2S3 glass

Low frequency Raman scattering and optical absorption edge were measured for As₂S₃ glasses quenched at temperature in the supercooling region of the glasses. It was found that both the Raman spectrum and the optical absorption edge shift to the lower energy side with the rise of the quenching temperature. The effects were interpreted in terms of the order of the arrangements of the layer-like clusters, which become more random as the quenching temperature goes higher.     

A pulsed EPR study of clustering of Yb ions incorporated in GeO2 glass

The structural aspects of clustering of Yb³⁺ ions and the paramagnetic behavior of these clusters have been investigated in GeO₂ glasses doped with 140-1100 ppm by weight of Yb₂O₃ using time-domain electron paramagnetic resonance (EPR) spectroscopic techniques. The echo-detected EPR (EDEPR) spectra of Yb³⁺ ions and their unusual dependencies on microwave power and magnetic field have been found to be indicative of the formation of clusters of these rare earth ions in GeO₂ glass that behave as non-Kramers type spin systems. The magnetic field and concentration dependence of phase relaxation rates of Yb³⁺ in these glasses further substantiate such a scenario and indicate the formation of clusters of Yb³⁺ ions. A comparison of the EDEPR spectra with calculated cw-EPR line shapes yields a semi-quantitative measure of the typical cluster size of ?3 Yb atoms and intra-cluster Yb-Yb distances of 3.5-4.0 Å in these glasses at doping levels of ?350 ppm of Yb₂O₃.     

Study of the structural insertion of Al in the Al2O3-SiO2 and Nd2O3-Al2O3-SiO2 glass systems

Glasses in the Al₂O₃-SiO₂ and Nd₂O₃-Al₂O₃-SiO₂ systems were prepared by the sol-gel method. The gel-glass evolution was studied using near-infrared (NIR) and ultraviolet-visible (UV-VIS) spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). The results obtained indicate a relationship between the sample compositions, the treatment temperature and the Al coordination. In the samples of the Nd₂O₃-Al₂O₃-SiO₂ system the densification of the structure, when the treatment temperature increases, leads to the segregation of neodymium oxide particles.