Formation of Color Centers in Glasses Exposed to Gamma Radiation

Glasses exposed to gamma radiation develop a visible absorption band similar to the F -band developed in alkali halide crystals. The function of cerium in preventing coloration of glass was studied in detail in an ultraviolet-transmitting phosphate base glass in which its characteristic absorption could be measured. When visible absorption was thus prevented, radiation still caused a strong absorption in the ultraviolet which was associated with the electronic structure of cerium. On this basis, transition ions of similar electronic structure were introduced. It was found that iron, manganese, cobalt, nickel, vanadium, copper, and, under certain conditions, some other elements do suppress the formation of the visible absorption band formed in the base glass by radiation while forming more or less prominent bands in other spectral regions. Thus the colorless iron phosphate glass remained colorless under radiation and could be considered to be "protected." Conversely, with cobalt the new band which reached into the visible was relatively intense and stable, suggesting its use to indicate radiation dose.     

Structural Role of Zinc Oxide in Silica and Soda-Silica Glasses

The structures of amorphous zinc silicate and sodium zinc silicate have been studied using the molecular dynamics computer simulation technique. Results showed that bond lengths and coordination numbers for the individual atomic species fit within the range of results from a number of crystalline and glassy silicates. Discrete ZnO₄ tetrahedra were seen to exist to a higher degree in the sodium zinc silicate system due to charge compensation from neighboring sodium atoms. Simulation results are also compared to EXAFS data of low concentrations of zinc oxide in silica and sodium silicate glasses. The local environment of oxygen in the simulated systems is also discussed.     

Optical and Thermal Bleaching of X-Irradiated Barium Aluminoborate Glasses

Photoproduction of interstitial atomic hydrogen centers (H⁰_i), apparently at the expense of boron electron centers (BEC) in barium aluminoborate glasses X-irradiated at 77 K, is reported. Electron paramagnetic resonance studies of isothermal and isochronal annealing of BEC and correlated decay of BEC with corresponding growth of H⁰_i under exposure of light were carried out. Some possible interactions between chemical states induced by irradiation are discussed.     

Color Centers in Sulfur-Doped Silica Glasses: Spectroscopic Manifestations of an SO2 Interstitial Molecule

The photoluminescence spectra of sulfur-doped silica glass upon excitation into the absorption band at 203 nm and a temperature of 10 K are investigated. It is revealed that the photoluminescence band with a maximum at about 420 nm and the photoluminescence excitation band have a resolved vibrational structure. A model is proposed according to which the bands of absorption at 203 nm and luminescence at 420 nm are assigned to SO₂ interstitial molecules that are weakly bound to the glass network (the transitions X ^~1 A ₁ C ^~1 B ₂ and a ^~3 B ₁ X ^~1 A ₁, respectively).     

Fluorescence Spectroscopy of Color Centers Generated in Phosphate Glasses after Exposure to Femtosecond Laser Pulses

A confocal fluorescence microscopy setup was used to observe, in situ , spectral changes in phosphate glasses which were modified using 0.3 μJ of tightly focused 800 nm, 130 fs laser pulses. On 488 nm excitation, the modified glass shows a broad fluorescence centered at roughly 600 nm, which decays with prolonged exposure to the 488 nm light. The decay behavior is dependent on the 488 nm power, with a faster decay rate for higher powers. A mechanism whereby color centers, formed by the femtosecond pulses, fluoresce when excited by the 488 nm light and are simultaneously photobleached is proposed to explain the observed behavior.     

Luminescence of Oxygen-Deficient Centers in Quartz Glasses

Glass Physics and Chemistry - This paper presents the results of studying the absorption, luminescence, and excitation spectra of oxygen-deficient centers (ODCs) in glasses obtained from quartz raw...     

Color Centers in Sulfur-Doped Silica Glasses: Spectroscopic Manifestations of an S 2 + Interstitial Molecular Ion

The absorption spectra of sulfur-doped silica glass are investigated under different external actions (laser irradiation, saturation of samples in a hydrogen atmosphere, and thermal annealing). It is found that the absorption band at 400 nm has a vibrational structure. A correlation between changes in the intensities of the absorption bands at 237 and 400 nm under different actions is revealed. Reasoning from analysis of the results obtained, a model is proposed according to which these bands are assigned to an S⁺ ₂ interstitial molecular ion. It is demonstrated that none of the optical centers considered in this work is responsible for the observed ESR signal.     

Titanium Centers Induced in Borate Glasses by Irradiation

The electron paramagnetic resonance of alkali borate glasses containing Ti was observed at 9.1 GHz before and after room-temperature X irradiation. The irradiation-induced spectra can be separated into (1) the well-known complex borate resonance with an average g value greater than that of the free electron (2.0028) and (2) a resonance with a lower g value. The latter resonance consists of two asymmetric ESR lines, one broad and the other narrow, whose characteristics are reported. These lines were not observed in the corresponding Ti-free base glasses; they arise from induced Ti centers. The broad asymmetric line ( T ₁) corresponds to a Ti^3.1 ion in sixfold coordination, whereas the narrow asymmetric line ( T ₂) corresponds to a Ti³⁺ ion in a different structural configuration. Lines T ₁ and T ₂ are stable at room temperature, not easily saturated with microwave power, and exhibit behavior independent of the complex borate resonance. The total relative intensity of these lines depends on the total Ti concentration in the glass, the Ti⁴⁺/Ti³⁺ ratio in the glass before irradiation, and the structure of the glass.     

Studies on Nonmetals During Irradiation: V, Growth and Decay of Color Centers in Barium Aluminoborate Glasses Containing Cerium

The radiation-induced absorption of a group of barium aluminoborate glasses was studied in a new facility for measuring optical absorption during irradiation with γ-rays. The results demonstrate that this technique provides significant new information on the kinetics of the radiation-induced coloring of glasses and suggest that most previous measurements are, at best, suspect. Barium aluminoborate glasses, both with and without Ce, were prepared under normal and reducing conditions. The coloring during irradiation and the decay after irradiation can be characterized by the absorption at 3.0 e V and at 2.25 or 1.90 e V. The Ce-free base glass continued to color as long as irradiated and, at a given dose, the absorption was at least 2 or 3 times that of the other glasses. The totally reduced 1% Ce glass colored to a constant level in the uv, but in the visible the coloring increased to a maximum and then decreased to a constant value. The partially reduced 1% Ce glass also colored to a constant value in the uv, but in the visible the original absorption decreased slightly. All the coloring curves recorded during irradiation are described accurately by expressions that include one or more increasing saturating exponential terms and may contain one linear or one decreasing saturating exponential term. After irradiation the coloring curves decrease and can be resolved accurately into one or more decreasing exponential components. Futhermore, all the observed coloring-curve features were derived from relatively simple kinetics.     

EPR and Kinetic Studies of Hydrogen Centers in Aluminoborate Glasses

Barium aluminoborate glasses containing hydrogen as an impurity, irradiated at 77 K with X rays, show the characteristic doublet of atomic hydrogen in the EPR spectra when measured at T<200 K. The hfs constant of the H^o_i center is smaller than that of free atomic hydrogen, indicating that the attractive van der Waals interaction is more important than the repulsive Pauli exclusion forces in that glassy matrix. It is suggested on the basis of isochronal and isothermal annealing experiments that there are at least three different sites for hydrogen, each one contributing with Ist-order decay kinetics. The activation energies found in 30 mol% BaO, 60 B₂O₃, 10 Al₂O₃ glass are, respectively, equal to E₁=(0.5±0.1), E₂=(0.24±0.03), and E₃=(0.16±0.03)×lO⁻¹⁹ J.     

Color Centers and Point Defects in Irradiated Thoria

The optical absorbance of commercially pure thoria single crystals was measured after oxidizing and reducing treatments, irradiation by 18-MeV protons, 48-MeV ¹⁶O ions, and ⁶⁰Co gamma photons, and thermal annealing at temperatures up to 950° C. For unirradiated specimens, absorption bands previously observed at 2.80, 3.03, and 4.03 eV were confirmed, and additional bands were identified at 1.67, 2.04, 2.45, 3.61, and 4.52 eV. Reduction and irradiation enhanced the 3.03 and 3.61 eV bands but diminished the 2.80, 4.03, and 4.52 eV bands. The centers responsible for the two groups of bands are thus presumed to be electron-type and hole-type, respectively. Impurity atoms, also, are probably involved in the centers. Ion irradiation produced an intense blue color in the exposed volume of the specimens, and additional absorption bands appeared at 1.49, 1.80, 2.03, and 2.32 eV. The behavior of these bands on annealing and on subsequent low-exposure gamma irradiation indicated that the corresponding centers are combinations of impurity atoms and oxygen interstitials.     

Color and Light Scattering of Platinum in Some Lead Glasses

The coloration and light scattering of sodium lead silicate, borate, and phosphate glasses containing platinum, introduced as PtCl₄, have been studied. Under the normal atmosphere of a furnace heated by silicon carbide elements, the platinum is retained in the colloidal state in the sodium lead silicates and borates, producing gray glasses. In the phosphate glasses yellow to orange ionic colors as well as grays are produced. Lead oxide increases the stability of platinum ions in the phosphate glasses. Under strong oxidizing conditions, ionic platinum also can be obtained in the borate and silicate glasses. Tyndall scattering can be detected in what appear to be clear, colorless glasses. This light scattering has been observed in some glasses containing as little as 1 p.p.m. platinum.     

铒掺杂锗酸盐玻璃的颜色可调上转换发光性质研究

研究了铒掺杂80GeO2-20R2O(R=Li,Na,K)玻璃在980nm激光器激发下的上转换发光性质.结果表明:玻璃发射出中心波长为525,546nm绿光和657 nm红光,分别对应Er3+的2H11/2→4I15/2,4S3/2→4I15/2和4F9/2→4I15/2的跃迁;红光和绿光的强度比例随着碱金属离子半径的...     

Aqueous Corrosion of Soda-Silica and Soda-Lime-Silica Glass

Corrosion of a 20Na2O-10CaO-70SiO₂ (mol%) glass by water was investigated using ir reflection spectroscopy, solution analysis, electron microprobe, and Auger electron spectroscopy. Corrosion proceeds at a much slower rate in the ternary glass than in a 20Na2O-80SiO2 glass. Within the Na-depleted layer of the ternary glass, a Ca-enriched zone develops—1500 A from the surface. The role of CaO in both the early and later stages of corrosion is discussed.     

Effect of TeO2 on Near‐Infrared Emission from Bismuth Centers in Borogermanate Glasses

Bi‐doped xTeO₂–(60?x)GeO₂–15B₂O₃–20MgO–5Al₂O₃ glasses were prepared by the conventional melt‐quenching method and their absorption and fluorescence spectra were characterized. Broadband near‐infrared (NIR) emission from Bi centers centered around 1240 nm with a full width at half maximum (FWHM) of 250 nm was observed, and the position of the emission peak strongly depends on the excitation wavelength. Increasing TeO₂ concentration results in the strong coloration of the glass, leading to the reduction and finally, complete quenching of the NIR emission. Based on Raman, X‐ray photoelectron spectroscopy and transmission microscopy observation, the coloration of the glass at high TeO₂ concentration can be ascribed to the precipitation of elemental Te nanoparticles of around 3–8 nm, which effectively suppresses the NIR emission by reabsorption. The precipitation of Te nanoparticles in an oxide glass may find novel applications in photonics and relevant fields.     

Phototropy of Reduced Silicate Glasses Containing the 570 m°Color Center

Simple silicate glasses of high purity and melted under strong reducing conditions develop a characteristic visible color center on absorbing ionizing radiation. This center peaks at 570 mμ in soda-silica glasses but changes position depending on the specific modifier ions. The center grows to relatively large concentrations in glass irradiated by long wavelength ultraviolet light but also decays rapidly at room temperature, imparting phototropic response to the glass. The 570 mμ center probably does not require specific ion impurities; however, minor additions of Ce, Eu, and Zr enhance its formation in certain base compositions. Transition series elements, even in small concentrations, inhibit the center. Sustained irradiation by ultraviolet light leads to lower equilibrium concentrations of the center and hence to fatigue of phototropic response.