Photoelastic response of alkaline earth aluminosilicate glasses

Understanding the structural origins of the photoelastic response in oxide glasses is important for discovering new families of zero-stress optic glasses and for developing a predictive physical model. In this Letter, we have investigated the composition dependence of the stress optic coefficient C of 32 sodium aluminosilicate glasses with different types of alkaline earth oxides (MgO, CaO, SrO, and BaO). We find that most of the composition dependence of the stress optic response can be captured by a linear regression model and that the individual contributions from the alkaline earths to C depend on the alkaline earth-oxygen bond metallicity. High bond metallicity is required to allow bonds to be distorted along both the bonding direction and perpendicular to it. These findings are valuable for understanding the photoelastic response of oxide glasses.     

On the relation between the gap,the transformation temperature and the average heat of atomization of As2Te3 glasses

The average heat of atomization of semiconducting glasses on the As₂Te₃ base, containing silicon, germanium and thallium is calculated from the heats of atomization of constituting elements. The average heat of atomization is correlated with the intrinsic energy gap and the transformation temperature of the studied glasses. The linear dependence between the energy gap, the transformation temperature and the average heat of atomization is found for As₂Te₃ glasses with silicon, germanium and thallium and is correlated with the binding energy between the constituting atoms.     

Impact of MoO3 concentration,frequency and temperature on the dielectric properties of zinc phosphate glasses

Phosphate glasses with the chemical composition of 47P₂O₅–24ZnO-(29-x)Na₂O-xMoO₃, x = 0, 2, 4, 6, 8 and 10, have been prepared using the melt quenching technique. Dielectric properties of these phosphate glasses are carried out in the frequency range from 1 to 100 kHz at different temperatures. Dielectric parameters such as dielectric constant ε′, dielectric loss ε′′ and ac conductivity of the investigated glasses have been evaluated. The dependences of these dielectric parameters on frequency, composition and temperature have been discussed. It is found that dielectric constant decreases with increasing frequency due to the reduction of space-charge polarization and dipole polarization. The dependence of ac conductivity on the MoO₃ content indicates a competition between electronic and ionic conduction. The temperature dependence of the dielectric parameters reveals a rising trend of the dielectric parameters with temperature. This rising trend is indicated due to the increase of the amplitude of the thermal vibration of the charge carriers which facilitates the electron hopping and drifting of the mobile ions. The linear trend of the ln(σ_ac)-1000/T plot indicates that ac conductivity of the investigated glasses is thermally-activated transport process and follows the Arrhenius equation. The activation energy and its composition dependence have been reported.     

Studies on electrical switching behavior of As-Te-Tl glasses – effect of local structure on switching type and composition dependence of switching voltages

Bulk As-Te-Tl glasses belonging to the As₃₀Te_70-xTl_x (4≤x≤22) and As₄₀Te_60-xTl_x (5≤x≤20) composition tie lines are studied for their I–V characteristics. Unlike other As-Te-III glasses such as As-Te-Al and As-Te-In, which exhibit threshold behavior, the present samples show memory switching. The composition dependence of switching voltages (V_t) of As-Te-Tl glasses is also different from that of As-Te-Al and As-Te-In glasses, and it is found that V_t decreases with the addition of Tl. Both the type of switching exhibited by As-Te-Tl glasses and the composition dependence of V_t, seems to be intimately connected with the nature of bonding of Tl atoms and the resultant structural network. Furthermore, the temperature and thickness dependence of switching voltages of As-Te-Tl glasses suggest an electro thermal mechanism for switching in these samples. PACS 71.55.Jv; 61.43Fs; 61.43.-j; 72.80.Ey; 73.61.Jc     

Ultrasonic attenuation in the amorphous dielectrics at low temperatures

The effect of the environmental vibrations on the tunneling in the two- level systems in glasses is discussed. It is shown that the temperature, frequency and other dependences of the tunneling constant are charged drastically due to this mechanism. This allows one to explain the peculiar temperature dependence of the ultrasonic attenuation in glasses in a wide temperature range.     

Temperature dependences of the order parameter for sodium nitrite embedded into porous glasses and opals

The temperature dependences of the order parameter η(T) for sodium nitrite NaNO₂ embedded in porous glasses with average pore diameters of 320 and 20 nm, as well as in artificial opals, have been investigated. It has been demonstrated that the dependence η(T) for sodium nitrite in the porous glass almost coincides with that for the bulk material, whereas this dependence for NaNO₂ in opals differs substantially from that observed in the bulk material and from those previously determined for sodium nitrite in porous glasses with average pore diameters of 3 and 7 nm. It has been revealed that the dependence of the order parameter for sodium nitrite in opals exhibits a temperature hysteresis (approximately equal to 8 K). The temperature dependence η(T) has been described using a simple model, which takes into account the nanopore diameter distribution existing in artificial opals.     

Physicotechnical and spectroscopic characteristics of titanium in aluminaphosphate phosphors

Aluminaphosphate glasses with different concentrations of matrix and activator components are prepared and investigated. The physicotechnical and spectral properties of titanium ions, the luminescence kinetics, and the dependence of these properties on the matrix composition in the glasses prepared are studied. The crystal field strength as a function of the Al₂O₃ content is determined. It is suggested that the octahedral coordination of the ions in these glasses is distorted.     

Application of the model of delocalized atoms to metallic glasses

The parameters of the model of delocalized atoms applied to metallic glasses have been calculated using the data on empirical constants of the Vogel–Fulcher–Tammann equation (for the temperature dependence of viscosity). It has been shown that these materials obey the same glass-formation criterion as amorphous organic polymers and inorganic glasses. This fact qualitatively confirms the universality of the main regularities of the liquid–glass transition process for all amorphous materials regardless of their origin. The energy of the delocalization of an atom in metallic glasses, Δε _e ≈ 20–25 kJ/mol, coincides with the results obtained for oxide inorganic glasses. It is substantially lower than the activation energies for a viscous flow and for ion diffusion. The delocalization of an atom (its displacement from the equilibrium position) for amorphous metallic alloys is a low-energy small-scale process similar to that for other glass-like systems.     

The temperature dependence of the magnetic susceptibility of spin glasses

The temperature dependence of the magnetic susceptibility of spin glasses is calculated exactly on the basis of a magnetic cluster model, following Néel. The susceptibility of a single cluster below its blocking temperature is taken to be negligibly small compared to its value above. A distribution of blocking temperatures may be obtained from observations on spin glasses. Conditions for the sharpness of the susceptibility peak are discussed and the low-temperature variation of the susceptibility is also obtained.     

Calculation of the Temperature Dependence of the Unrelaxed Shear Modulus of High-Entropy Bulk Metallic Glasses from Calorimetric Data

JETP Letters - A method is proposed to calculate the temperature dependence of the unrelaxed shear modulus of high-entropy bulk metallic glasses from differential scanning calorimetry data. The...     

Small-angle X-ray scattering study of the structure of glassy nanoporous matrices

The structure of high-silica glassy nanoporous matrices prepared from two-phase glasses has been investigated using the small-angle X-ray scattering technique. Parameters of materials, such as the density, porosity, specific surface area, average nanopore radius, average radius of scattering particles filling the pore space, and their fractal dimensions, have been determined. The dependence of the obtained structural parameters on the conditions of chemical treatment of glasses has been established. It has been demonstrated that the results obtained are in good agreement with porosimetry and electron microscopy data.     

Nonuniversal features of the ac conductivity in ion conducting glasses

Recently, Sidebottom [Phys. Rev. Lett. 82, 3653 (1999)] proposed a new scaling approach for the conductivity spectra of ion conducting glasses. This approach is based on the condition that the shape of the spectra is universal. In this Letter, we show that this condition is generally not fulfilled, but that the shape depends on the glass composition. In single alkali glasses, the frequency dependence of the conductivity varies with the alkali oxide content. Furthermore, the mixing of dissimilar alkali ions leads to pronounced changes in the shape of the conductivity spectra.     

One and two-photon absorption in multicomponent glasses and the measurement of cubic nonlinear susceptibility

One-and two-photon absorption of N₂-laser radiation (λ = 337 nm) in multicomponent silicate and phosphate glasses is investigated. A monotonic decrease from pulse to pulse in the intensity of radiation passing through a sample and in the luminescence excited by this radiation is found. The possibility of calculating the imaginary part of the cubic nonlinear susceptibility of glasses using the time dependence of the change in the laser intensity at the sample output is shown.     

The luminescence of glasses activated with terbium

The absorption and luminescence spectra of borate, phosphate, and silicate glasses and their dependence upon the activator concentration and the temperature were studied. The luminescence mechanism was investigated. The spectra were analyzed, taking into account the composition and structure of the glasses. The term scheme of the trivalent terbium in the glasses was constructed. The conditions for stimulated radiation in glass activated with terbium are outlined.Reported at the 12th Conference on Luminescence, L'vov, 1964.     

Compositional dependences of average positron lifetime in binary As-S/Se glasses

Compositional dependence of average positron lifetime is studied systematically in typical representatives of binary As-S and As-Se glasses. This dependence is shown to be in opposite with molar volume evolution. The origin of this anomaly is discussed in terms of bond free solid angle concept applied to different types of structurally-intrinsic nanovoids in a glass.     

Mössbauer studies of iron-rich metallic glasses

Iron-based metallic glasses have recently become an important class of ferromagnetic materials exhibiting excellent soft magnetic properties coupled with good mechanical properties. These glasses are usually prepared by rapid quenching techniques and are produced in thin long ribbon form with widths ranging from a few mm to 150 mm or more.⁵⁷Fe Mössbauer spectroscopy has been extensively used to study hyperfine interaction parameters in these metallic glasses to understand ferromagnetism in amorphous structure. In particular, Mössbauer spectra have been carefully analyzed to reveal information about the distribution of hyperfine fields resulting from the randomness of the atomic arrangement and to understand the temperature dependence of hyperfine fields, spin-wave excitations, magnetic structure, thermal stability and crystallization, the quenched-in magnetization axis, the Curie temperature and its dependence on compositions, the effect of stress and pressure on the magnetic properties, corrosion behaviour, local order and atomic arrangement, phase transformation, etc. This paper reviews the application of⁵⁷Fe Mössbauer spectroscopy to magnetic studies on metallic glasses mainly based on the iron-boron alloy system, and some of the significant results obtained which are characteristic of the glassy/amorphous state.     

Nuclear quadrupolar spin-lattice relaxation in the amorphous state

It is proposed that the nuclear quadrupole spin-lattice relaxation in glasses is due to interaction of solitons with the nuclear quadrupole moment. The magnitude of the interaction is estimated and the resulting temperature dependence of the spin-lattice relaxation time is compared to experiment.     

A theory of electrical conductivity in metallic glasses

In this paper is presented a phenomenological theory of electrical conductivity in metallic glasses based on the method of so-called modified relaxation time (till now applied to semi-conductive glasses only). The essential difference consists of a consistent use of Fermi-Dirac statistics because of the degeneracy of electron gas. The results that this theory yields obviously elucidate the existence of both positive and negative values of the resistivity coefficient in metallic glasses and lead to the conclusion that the minimum in the temperature dependence of electrical conductivity may not be necessarily related to the so-called Kondo effect. This is a simple consequence of the interaction between positive (metallic) and negative (semiconducting) contributions to the electrical conductivity which appears in the metallic glasses due to disorder.     

Frequency dependence of the AC susceptibility of a cobalt aluminosilicate glass

The frequency dependence of the ac susceptibility for an aluminosilicate glass containing 14.3 at% cobalt has been measured over six decades in frequency. A very strong frequency dependence of _χ(T) is observed both around and below the freezing temperature in contrast to the transition metal spin glasses. Possible reasons for these differences are discussed.     

Y共掺对掺Er硅酸盐玻璃光致荧光及荧光寿命的影响

采用固相反应方法制备了Er/Y共掺激光玻璃，其中Er³⁺浓度分别为0.5at%和1.0at%，所对应的Y³⁺浓度的变化范围分别为0.0at%—2.5at%和0.0at%—5.0at%.通过吸收光谱、瞬态和稳态光致发光光谱测量，研究了Y共掺对Er³⁺吸收截面、发射截面、荧光寿命和光致荧光特征的影响.研究结果表明：Y共掺杂导致1530nm附近的吸收峰宽化，对Er³⁺的吸收起到了一定的增强作用，并且这种宽化作用随着Er关键词： Er/Y共掺玻璃 光致荧光 荧光寿命