Morphology of swift heavy ion tracks in metallic glasses

Swift heavy ion irradiated metallic glasses were studied using synchrotron based small angle X-ray scattering (SAXS). Ribbons of Fe₈₀B₂₀, Fe₈₅ B₁₅, Fe₈₁B_13.5Si_3.5C₂ and Fe₄₀Ni₄₀B₂₀ were irradiated with 11.1 MeV/nucleon (MeV/u) ¹³²Xe, ¹⁵²Sm, ¹⁹⁷Au and 8.2 MeV/u ²³⁸U ions to fluences between 1 × 10¹⁰ and 1 × 10¹² ions/cm². The SAXS measurements provide evidence for the formation of ion tracks and allow a quantitative analysis of the track ensemble in all studied materials. The ion tracks have been well described by cylinders with abrupt boundaries and an electronic density change of (0.03 ± 0.01)% between track and matrix material. An inelastic thermal spike model was fitted to the experimental track radii to determine the critical energy density required to create an ion track. Despite the similar energy loss and track cross-sections, 30% higher track creation threshold is apparent for the binary alloys.     

Irradiation-induced change of valence of Cr3+ ions doped in alkali sulphates

It is shown by means of investigation of both optical absorption spectra and Roentgen K-lines of chromium doped in LiKSO₄, LiNaSO₄, and Li₂SO₄ · H₂O crystals, that X-irradiation results in change of the impurity charge in a following way: Cr³⁺ + h → Cr⁴, Cr⁴⁺ + h → Cr⁵⁺.     

Triple-crystal X-ray spectroscopy of diffuse scattering from tracks

A theoretical model is presented for studying the structure of tracks of charged particles in crystals. Two structurally different track regions are considered: the track proper and its elastically deformed vicinity. A computer program is written for determining the contributions from a track and its elastically deformed vicinity to the experimental diffuse-scattering data and their quantitatively evaluating dimensions and other parameters. The effect of the model parameters on the shape of diffuse-scattering curves is also considered.     

Influence of disorder on the diffusion of alkali ions in SiO2- and GeO2-glasses

The frequency factor and activation energy for the diffusion of Na and K in SiO₂-glasses are strongly dependent on the concentration of Na₂O or K₂O respectively. A similar behavior was found for hydrogen diffusion in amorphous metals. In the last case the results are in agreement with theoretical calculations, if a Gaussian distribution of activation energies is assumed which arises from a similar distribution of the potential energy of hydrogen being in equilibrium sites. The equations derived were used in this study to describe the concentration dependence of Na and K diffusion in SiO₂ glasses, because these impurities are dissolved in randomly distributed interstices of different volume as well. The theory yields the two experimental facts that diffusion below the glass transformation temperature is governed by a single activation energy and that concentration profiles of the tracer atoms can be described by a constant diffusion coefficient. A comparison with low temperature results for Na diffusion shows they agree with theoretical predictions and yield the following parameters: most probable value of the activation energy = 59.4 kJ/mol, corresponding frequency factor = 2 × 10^?3 cm²/s and half width of the Gaussian distribution = 25 kJ/mol. The model also predicts a minimum in plots of the chemical diffusivity versus concentration which is in agreement with experimental findings for sodium diffusion in GeO₂.     

Irradiation-induced changes in the local environment of Si and Al in LnSiAlON glasses as probed by Al and Si NMR

Two compounds have been studied: an oxide glass from the Y-Si-Al-O system and an oxynitride glass from the Y-Si-Al-O-N system, both bombarded with Sn-ions (975 MeV, fluences ranging from 10¹² to 2.7 × 10¹³ Sn/cm²). The changes in the environment of the silicon and the aluminium were investigated using NMR spectroscopy. Irradiation by Sn ions leads to a loss of nitrogen in the silicon and probably the aluminium environments. Part of the aluminium changes from a network former coordination to a network modifier coordination while the oxide silicate network exhibits a higher cross-linking due to an increase of the population of bridging oxygen. Part of the aluminium in five-fold coordination is formed at the expense of aluminium in six-fold coordination in the case of the oxynitride glass and the changes in the silicon environment occur at lower fluences than for the oxide glass.     

Determination of thermal diffusion coefficient and diffusion coefficient

A new technique is described to determine the thermal diffusion coefficient, D', and the difusion, D, of Fe, Si and Al in liquid Mg. This technique is based on a boundary condition, formulated by including contributions of temperature and cocentration gradients in the liquid to the advancing solid-liquid interface during unidirectional solidification of a binary alloy. The determined values of D'_Fe, D'_Si and D'_Al are 5.57 × 10^-6, 7.35 × 10^-6 and 3.64 × 10^-6 cm/sec °C and D_Fe and D_Si are 1.9 × 10^-5 and 1.5 × 10^-5 cm²/sec, respectively.     

Sodium diffusion in boroaluminosilicate glasses

Understanding the fundamentals of alkali diffusion in boroaluminosilicate (BAS) glasses is of critical importance for advanced glass applications, e.g., the production of chemically strengthened glass covers for personal electronic devices. Here, we investigate the composition dependence of isothermal sodium diffusion in BAS glasses by ion exchange, inward diffusion, and tracer diffusion experiments. By varying the [SiO₂]/[Al₂O₃] ratio of the glasses, different structural regimes of sodium behavior are accessed. We show that the mobility of the sodium ions decreases with increasing [SiO₂]/[Al₂O₃] ratio, revealing that sodium is more mobile when it acts as a charge compensator to stabilize network formers than when it acts as a creator of non-bridging oxygens on tetrahedrally-coordinated silicon and trigonal boron. The impacts of both the addition of iron and its redox state on the sodium diffusivity are explored in terms of the structural role of ferric and ferrous ions. By comparing the results obtained by the three approaches, we observe that both the tracer Na diffusion and the Na–K interdiffusion are significantly faster than the Na inward diffusion. The origin of this discrepancy could be attributed to the fact that for sodium inward diffusion, the charge compensation for electron holes is a rather slow process that limits the rate of diffusion.     

Inward cationic diffusion in glass

We report that inward diffusion of network-modifying divalent cations can occur in iron-containing silicate glasses when they are treated in a reducing atmosphere near the glass transition temperature. As a result of the inward diffusion, a silica-rich nanolayer forms on the glass surface, which increases the hardness and chemical durability. The thickness of the layer can be controlled by varying the heat-treatment conditions. We clarify the mechanism of the inward diffusion and calculate the diffusion coefficient for the network-modifying divalent cations. We demonstrate that the diffusion of these ions is the rate-limiting factor for the reduction process.     

Luminescence of Cu ions in phosphate glass

Time-resolved fluorescence and lifetime measurements of Cu⁺ ions in phosphate glass with different copper concentrations have been performed at room temperature and 77 K. The experimental results are explained by energy transfer.     

Effect of Fast Electron Irradiation and Annealing on the Luminescence in GaAs(Zn) crystals. Irradiation-induced 1.26 and 1.39 eV Emission Bands

The effect of 2.2 MeV electron irradiation and subsequent annealings on the photoluminescence in zinc-doped p-type GaAs crystals is studied and analyzed. Rather strong emission bands peaked at hv_m (77 K) near 1.26 eV (induced by electron irradiation) and 1.39 eV (induced by annealing of irradiated crystals) are observed. Evidence is presented that the 1.26 and 1.39 eV emission bands occur due to radiative electronic transitions in As_iZn_Ga and V_AsZn_Ga pairs induced by irradiation and annealing of irradiated crystals, accordingly. The observed variations in the intensities of the 1.26 and 1.39 eV emission bands upon irradiation and subsequent annealings of GaAs(Zn) crystals are explained in terms of irradiation and annealing-induced variations in the amount of 1.26 and 1.39 eV radiative centres resulting from: a) the effective interaction of mobile radiation-induced defects in the arsenic sublattice with zinc atoms leading to the formation of As_iZn_Ga and V_AsZn_Ga pairs; b) the thermal dissociation of As_iZn_Ga and V_AsZn_Ga pairs on individual components.     

Radiation-enhanced diffusion of Na in alkaline glasses

The surface Na concentration of glass is found to increase under X-ray flux. The experimental data are well fitted by a first-order rate equation and are interpreted on the basis of radiation-enhanced diffusion mechanism of the Na with a coupling between material and defect fluxes.The Na concentration-versus-depth profiles show that the phenomenon also takes place at depth greater than the XPS sampling depth. Moreover, there is some evidence that in addition to diffusion from the bulk, surface segragation also occurs.     

Impurity diffusion of 114In in Cu

Using the tracer-standard sectioning technique the impurity diffusion of indium in copper has been investigated in the temperature range from 798.1 to 1081.0°C. For the frequency factor and the activation energy, respectively, the following values were determined: D₀₂ = 1.87 cm² · s⁻¹; Q₂ = 2.034 eV. The results are compared with predictions of theoretical models of the impurity diffusion in metals.     

Cation diffusion in soda-lime-silicate glass melts

Cation diffusion was experimentally investigated in soda-lime-silicate glass melts (composition in mol%: 74SiO₂–16Na₂O–10CaO) at temperatures from 1000 to 1200 °C using the diffusion couple technique. One half of each diffusion couple was doped with 11 trace elements (500 ppm by weight of Rb, Cs, Sr, Zn, Cd, Nd, Eu, In, Sn, Ge and 1000 ppm by weight of Fe). Experiments were performed in an internally heated gas pressure vessel at a confining pressure of 100 MPa to avoid convective fluxes in the diffusion samples. The distribution of major elements was analyzed by electron microprobe. IR spectroscopy was used to quantify concentrations of dissolved water in the run products. Trace element diffusion profiles were measured simultaneously employing synchrotron X-ray fluorescence microanalysis. In all analyzed glasses the highest diffusion coefficients were observed for Rb whereas Nd was always the slowest element, e.g. at 1000 °C the diffusivity decreases from (1.51 ± 0.35) × 10⁻¹¹ m²/s for Rb to (1.29 ± 0.34) × 10⁻¹³ m²/s for Nd. The diffusivity of Nd is close to the chemical diffusivity of network former calculated from viscosity data using the Eyring relationship. Surprisingly, the rare earth elements Nd (3+) and Eu (mixed 2+, 3+) diffuse more slowly than the tetravalent Ge. Activation energies for diffusion increase from (132.1 ± 1.5) kJ/mol for Rb to (205 ± 16) kJ/mol for Eu. Based on the diffusion data for Eu, Sr and Nd we estimated that Eu²⁺/Eu_total ratios in soda-lime-silicate glass melts are below 0.04 both at reducing and oxidizing conditions.     

The role of iron ions in laser ruby

Doping possibility of long ruby crystals grown by Czochralski method under reducing protective atmosphere by iron ions in described. Using the admixture of hydrocarbons to the protective atmosphere this dopage may be realized. Iron ions increases damage threshold of the Q-switched laser ruby rods.     

Spin state of cobalt ions in NdCoO3

The crystal structure of NdCoO₃ is studied by neutron diffraction. It is shown that static cooperative Jahn—Teller distortions are absent up to the temperature of transition to the metallic state. The results are discussed within the model considering the transition of cobalt ions from the low-spin to the intermediate-spin state by gradual thermal excitation without a clearly pronounced critical behavior.     

Spectroscopy of transition metal ions in inorganic glasses

Transition metal (TM) ions have been used as colouring agents in the glass industry for a long time. Recently, great attention has been paid to the TM ion doped glasses for the development of new lasers or luminescence materials. The absorption spectra of TM ions in different kinds of glasses have been studied extensively, but little work has been done for fluorescence and relaxation spectra. In this paper emphasis is laid on analysing the influence of chemical bond characteristics of the base glass on the spectra and the site structure of transition metal ions in glasses. Recent experimental results about the luminescence characteristics of low valence ions (such as Ti³⁺, Cr³⁺, V²⁺, Mn²⁺, Cu⁺, Mo³⁺) in glasses are also reported.     

Energy spectrum of uranyl ions in soda-lime glass

The wide band structures observed in the absorption spectrum and the fluorescence spectrum induced by a broad-band light source are the superpositions of narrower bands associating with different non-interacting uranyl molecular systems in glass. When the uranyl molecular systems are selectively excited by narrow-band light sources, the bandwidths of the fluorescence decrease. Furthermore, fluorescence showed multiplet structures and shifting of these structures when the excitation wavelength was varied, particularly, between 5100 and 5250 Å. By means of selective excitation and correlation between excitation energy and fluorescence energy, the first absorption band in the visible region has been analyzed to be the superposition of six narrower bands.