A Gamma-Ray Induced Absorption Band in Some Lead Borate Glasses

Observations made on some lead borate, lead aluminoborate, and lead boroaluminosilicate glasses have shown that an absorption band is induced at 1.5 e.v. (825 mμ) by gamma irradiation. Experimental evidence indicates that this band is associated with Pb²⁺ ions and boron in the structure of these glasses. On replacing PbO by Tl₂O in a borate glass, two strong bands were observed; one band corresponds to the 1.5 e.v. band induced in lead borate glasses and a completely new band at 1.0 e.v. (1235 mμ). A postulate for the center responsible for the absorption band at 1.5 e.v. is proposed.     

Lead Chalcogenide Quantum Dot-Doped Glasses for Photonic Devices

Tunable absorption and photoluminescence (PL) of lead chalcogenide quantum dots (QDs) doped in glasses due to the quantum confinements effect have been actively investigated for application as saturable absorbers, laser sources, and fiber-optic amplifiers. Optical properties of QDs have been carefully monitored by controlling their sizes through heat treatment and rare-earth ion doping. Two- and three-dimensional precipitation of lead chalcogenide QDs were also realized using silver ion exchange and femtosecond laser irradiation in combination with thermal treatment. Prototypes of microstructured single-mode fibers and tapered fiber amplifiers containing QDs proved potentials of these materials for fiber-optic amplifiers application. Further research works on QD-doped solid core fibers, surface passivation of quantum dots and their application for the mid-infrared optical devices are necessary.     

UV-Visible and IR Spectroscopic Studies of Gamma Irradiated Transition Metal Doped Lead Silicate Glasses

Lead silicate (LS) glasses of the basic composition PbO 75%, SiO₂ 25% together with samples containing (∼0.1%) of transition 3d metal oxides (Ti→Cu) were prepared. UV/VIS optical analysis for as prepared and after successive gamma irradiated samples were used to shed more light on the structural modifications that occur due to different dopants and different irradiation doses. The UV-Vis. spectral analysis for undoped glass shows induced absorption bands at 205–400 nm which are assumed to be correlated with the base host glass and dopant transition metal ion doped glasses and dose of irradiation. The positions of the bands are observed to change slightly by gamma irradiation due to the combined effect of induced defects from the host base glass or the transition metal added. Gamma irradiation is observed to cause a decrease in the intensities of the IR absorption bands of the prepared samples accompanied by losing sharpness. These features are related to more amorphicity or disorder by irradiation or to the possible changes in bond angle or bond length in the building groups arrangement.     

Interaction of Gamma Rays with Calcium Aluminoborate Glasses Containing Holmium or Erbium

The optical absorption spectra of nominally pure and rare-earth-ion-doped (Ho³⁺ or Er³⁺) calcium aluminoborate (cabal) glasses were measured from 190 to 900 nm before and after γ-ray irradiation. The induced absorption spectra, calculated as the difference between the spectra of the irradiated and the unirradiated glasses, exhibit the characteristic absorption bands caused by the respective rare-earth ions. The intensity of the induced bands depends on the rare-earth oxide content. The response of the cabal glass to γ-ray irradiation is related to the formation of color centers associated with the intrinsic defects in the lattice structure of the cabal glass. The rates of formation and annihilation of the color centers are believed to approach saturation or equilibrium with prolonged irradiation.     

Shielding Behavior of Gamma-Irradiated MoO<Subscript>3</Subscript> or WO<Subscript>3</Subscript>-Doped Lead Phosphate Glasses Assessed by Optical and FT Infrared Absorption Spectral Measurements

Undoped and MoO₃- or WO₃- doped lead phosphate glasses were prepared by the melting-annealing technique. The glasses were characterized through UV-visible and infrared measurements which were repeated after gamma irradiation. Optical spectrum of binary lead phosphate glass shows distinct ultraviolet bands correlated with unavoidable trace iron impurities within the chemicals used for the preparation of the glasses. UV-visible absorption spectra of MoO₃- or WO₃- doped glasses exhibit additional UV-visible bands which are related to the presence of four oxidation states of the two transition metal (molybdenum or tungsten) ions (Mo³⁺, Mo⁴⁺, Mo⁵⁺, Mo⁶⁺, W³⁺, W⁴⁺, W⁵⁺, W⁶⁺). The extra UV band is related to hexavalent (5d⁰) state while the rest of the visible bands are related to (350–440 nm - trivalent state), (450, 550, 650 nm - tetravalent state) while the broad band centered at about 770 nm (pentavalent state). The intensities of the absorption bands are observed to change with the transition metal content and their valencies. Infrared absorption spectra reveal distinct vibrational bands which are assigned to phosphate groups with sharing of Pb-O vibrations within both the range 460–620 cm^-1 and the range 900–1100 cm^-1 revealing a compact network structure. Gamma irradiation causes a minor increase in intensity of one of the UV band due to suggested photo-oxidation of some trace ferrous ions to additional ferric ions but the remaining spectral curve remains unaffected which is obviously related to some shielding effects of heavy atomic weight of PbO. This heavy metal oxide (PbO) is assumed to retard or prohibit the free passage of free electrons or positive holes generated during the irradiation process.     

Interaction of γ-rays with Some Alkali-Alkaline-Earth Borate Glasses Containing Chromium

The change in the visible spectra of some irradiated ternary borate glasses containing chromium has been studied by increasing the γ-ray doses with changing alkali content or increasing chromium concentration. In the glass without chromium, the γ-rays induce two absorption bands which are attributed to the formation of positive hole centers, whereas in the glass containing chromium at least three absorption bands are observed. The results showed that the visible absorption bands before and after γ-ray irradiation exhibited changes with the radiation dose and/or the chemical composition of the glass. The response of the glasses to γ irradiation is related to the creation of defect color centers, the approach of a saturation condition, and the possible photochemical effect on the transition metal.     

含铅玻璃及其无铅化的研究

介绍了铅对人体的危害,综述了一些为限制铅的使用及排放而制定的相关法规,详细介绍了铅玻璃在现阶段中的一些主要用途和目前人们对这些玻璃的无铅化方面的工作。指出电子产品无铅化的迫切性。     

Structural and Optical Properties of Lead-Boro-Tellurrite Glasses Induced by Gamma-Ray

Spectrophotometric studies of lead borotellurite glasses were carried out before and after gamma irradiation exposure. The increasing peak on the TeO₄ bi-pyramidal arrangement and TeO₃₊₁ (or distorted TeO₄) is due to augmentation of irradiation dose which is attributed to an increase in degree of disorder of the amorphous phase. The structures of lead tellurate contain Pb₃TeO₆ consisting of TeO₃ trigonal pyramid connected by PbO₄ tetragonal forming a three-dimensional network. The decrease of glass rigidity is due to irradiation process which is supported by the XRD diffractograms results. The decreasing values of absorption edge indicate that red shift effect occur after irradiation processes. A shift in the optical absorption edge attributed to an increase of the conjugation length. The values of optical band gap, E_opt were calculated and found to be dependent on the glass composition and radiation exposure. Generally, an increase and decrease in Urbach’s energy can be considered as being due to an increase in defects within glass network.     

Spectroscopic Inquiry of the Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-role in Binary Sodium Borate,Sodium Silicate and Sodium Phosphate Glasses and Effects of Gamma Irradiation

Optical absorption spectral investigations have been carried out on Fe³⁺ ions doped sodium borate, sodium silicate and sodium phosphate glasses before and after gamma irradiation. The UV-visible absorption spectrum exhibits bands characteristic of Fe³⁺ ions coordination in each system. Interesting aspects of FT-IR spectra were found, and this gives information about the structure changes in the constituent units of these glass systems as a function of Fe₂O₃ concentration. All glasses reveal characteristic absorption bands due to the addition of different ratios of iron which explain the state of iron in each system in terms of its valence and coordination number. Results indicate that iron favors a higher oxidation state (tetrahedral coordination) in the case of sodium silicate glasses. The doping with progressive Fe₂O₃ additions (0.5?7.5 %) has some effect on the number and position of the characteristic bands due to formation of FeO₄ groups. The IR absorption spectra after irradiation reveal limited changes in the intensity which can be correlated with minor changes in bond angles and /or bond lengths within the structural units by irradiation.     

Leaching of Lead and Connectivity of Plumbate Networks in Lead Silicate Glasses

The formation of a plumbate network in binary lead silicate glasses was examined based on the leaching behavior of Pb²⁺ in lead silicate glasses over a wide composition region. The effective diffusion coefficient of Pb²⁺ at 40°C was on the order of 10⁻¹⁷ m²/s for PbO<35 mol% glasses, and increased three orders of magnitude for 35–50 mol% PbO contents. Such a steep composition dependence is considered to be because of changes in the medium or longer range structure. That is, it is proposed that the plumbate network forms a percolative 3D network in the composition region to form diffusion paths for the lead ions. In addition, the present results indicate that the lead ion exists as a network former over the entire glass forming composition range of the binary silicate glasses.     

Effect of CoO and Gamma Irradiation on the Infrared Absorption Spectra of Lithium Borate Glasses

Undoped and cobalt-doped lithium borate glasses (LBG) of various compositions, by varying cobalt contents were prepared by a conventional melt quenching technique. The density and molar volumes of the glass samples were estimated and; infrared absorption spectra were measured in the spectral range 400–1600 cm^?1before and after an irradiation dose of 50 kGy and 200 kGy. Experimental results showed that the density of studied samples increased as CoO increased while the molar volume decreased. FT-IR spectra of the prepared samples have been analyzed by the deconvolution of the spectra. A deconvolution technique is presented to make use of the BO₄ data and follow the change in the modifier and former fractions of CoO. FTIR was also used to study the glass system before and after gamma irradiation. The experimental results clearly indicate that after irradiation a significant change in the structure of the LBG glass network is observed. The modifying action of CoO on the glass composition is also studied. The glasses doped with 5 wt% of CoO are relatively more radiation resistant than the other compositions.     

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.     

Correlation between Macro- and Microstructural Changes in Ge:SiO2 and SiO2 Glasses under Intense Ultraviolet Irradiation

The photochemical transformation mechanism of defects in germanosilicate and silica glasses under ultraviolet (UV) laser irradiation has been investigated based on the changes in Raman spectra before and after irradiation. Two types of silica glasses, fused silica (type I) and dry synthetic silica (type IV), and germanosilicate optical fiber preforms were irradiated by intense UV photons from excimer lasers. Spectral changes in optical absorption and Raman spectra were examined to clarify a correlation between the microscopic defect formation and the macroscopic structural changes causing a photorefractive effect. Successive generation of E' centers through divalent centers is closely correlated with changes in Raman spectra, indicating that large structural changes in the glass network involved in this process would be the origin of photon-induced densification of the glasses. In addition, it has been proposed that the successive generation of E' centers is mediated by transient divalent centers converted from relaxed cation homobondings.     

‘Optical and FT Infrared Absorption Spectra of Soda Lime Silicate Glasses Containing nano Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> and Effects of Gamma Irradiation

The optical absorption spectra of undoped soda lime silicate glass together with two glasses doped with either (1 % nano Fe₂O₃ ) or with both (1 % Nano Fe₂O₃ + 5 % cement dust) have been measured from 200 to 2400 nm before and after gamma irradiation with a dose of 8 Mrad. The undoped glass reveals strong UV absorption with two distinct peaks which are attributed trace ferric iron ions present as impurity. Upon gamma irradiation , this base glass exhibits three peaks at 240,310 and 340 nm and the resolution of an induced broad visible band centered at 530 nm. The two doped glasses show an additional small visible band at about 440 nm and followed by a very broad band centered at 1050 nm. Upon gamma irradiation, the two doped samples reveal the decrease of the intensities of the spectrum. The two additional bands are related to ferric (Fe⁺³) ions to the band at (440 nm) while and the broad band at 1050 nm is due to ferrous iron (Fe⁺²) ions. The decrease of the intensities of the UV-visible spectrum upon irradiation can be related to of capturing freed electrons during irradiation . Infrared spectra of the glasses reveal repetitive characteristic absorption bands of silicate groups including bending modes of Si–O–Si or O–Si–O, symmetric stretching , antisymmetric stretching and some other peaks due to carbonate , molecular water , SiOH vibrations . Upon gamma irradiation, the IR spectra reveal a small change in the base spectrum while the IR spectra of the two doped glasses remain unchanged. The change of the IR spectrum of the base glass is related to suggested changes in the bond angles or bond lengths of the mid band structural units. The doped glasses show resistance to gamma irradiation because the nano Fe₂O₃ can capture released electrons and positive holes.     

Microseparation in Lead Borate Glasses

The microstructure of a series of lead borate glasses was studied by electron microscopy and small-angle X-ray scattering techniques. Although the glasses were optically homogeneous, microheterogeneities of the order of 2000 to 3000 A were detected in glasses with compositions near the region of two-liquid stability. The size of these heterogeneities increased as the composition approached the region of immiscibility.     

Effect of Gamma Radiation on Optical and EPR Absorption Spectra of Phosphate and Fluoride Glasses Containing Lead

The induced optical and EPR absorption spectra of phosphate and fluoride glasses containing lead are investigated. It is revealed that exposure to gamma radiation leads to the formation of radiation-induced defects responsible for the induced absorption band with a maximum at 12500–13500 cm⁻¹ and the EPR signal in the form of an almost symmetric line with a g factor of 1.999 and a linewidth of ≈26 Oe. Analysis of the intensities of the absorption bands and the EPR signals in the spectra of glasses with low terbium, tin, and carbon contents and the study of their thermal bleaching demonstrate that the color centers are electron traps, whereas the paramagnetic centers are hole-trapping centers. Examination of the change in the parameters of the absorption bands in the spectra of glasses with different R ₂O contents (R = Na, K, Rb, Cs) makes it possible to determine the location of the color centers associated with the Pb⁺ ions in the structure. It is established that the glasses under investigation are characterized by the nonlinear absorption of radiation at a wavelength of 1.06 μm. The mechanism of formation of radiation-induced defects is considered. Original Russian Text Copyright ? 2005 by Fizika i Khimiya Stekla, Bocharova, Karapetyan.     

Interaction of radiation-induced defects of glasses with CdSe and CdS nanocrystals

The influence of X-ray irradiation on the absorption spectra of commercial light filters based on the glasses containing selenium, cadmium, and sulfur has been investigated. The light filters were preliminary subjected to the heat treatment, which resulted in the precipitation of nanocrystals in the glass matrix. The irradiation leads to stationary partial bleaching of glasses. Analysis demonstrates that the difference spectra contain the induced absorption bands of conventional radiation-induced color centers of alkali silicate glasses and a fine structure. The fine structure closely resembles the known difference spectra obtained under the action of the external constant or low-frequency alternating electric field on glasses containing CdSe nanocrystals. The conclusion is drawn that the stable radiation-induced centers of the glass at the interface with nanocrystals serve as a source of the Coulomb field affecting the energy levels of the size quantization of the nanocrystals. It is suggested that nanocrystals of the type of the CdS_xS_1−x solid solutions in these glasses are either lacking or do not manifest themselves in the spectra after irradiation.     

微波消解-原子吸收法快速测定汽油中的锰铅铁

提出了微波消解-原子吸收法测定汽油中锰、铅、铁的分析方法。汽油样品用硝酸和少量高氯酸(混酸)做溶剂经过60℃水浴预处理后。在密闭容器中进行消解,样品溶解完毕泄压后,定容,用原子吸收仪器自有的快速序列分析功能的同时测定锰、铅、铁的含量,快速高效。同时考察了微波消解称样量、溶剂用量及共存离子对分析结果的影响,其标准样品的测定结果与标准值一致。本法适应于汽油中锰、铅、铁的测定。     

Interaction of radiation-induced defects of glasses with CdSe and CdS nanocrystals

The influence of X-ray irradiation on the absorption spectra of commercial light filters based on the glasses containing selenium, cadmium, and sulfur has been investigated. The light filters were preliminary subjected to the heat treatment, which resulted in the precipitation of nanocrystals in the glass matrix. The irradiation leads to stationary partial bleaching of glasses. Analysis demonstrates that the difference spectra contain the induced absorption bands of conventional radiation-induced color centers of alkali silicate glasses and a fine structure. The fine structure closely resembles the known difference spectra obtained under the action of the external constant or low-frequency alternating electric field on glasses containing CdSe nanocrystals. The conclusion is drawn that the stable radiation-induced centers of the glass at the interface with nanocrystals serve as a source of the Coulomb field affecting the energy levels of the size quantization of the nanocrystals. It is suggested that nanocrystals of the type of the CdS_xS_1−x solid solutions in these glasses are either lacking or do not manifest themselves in the spectra after irradiation.     

Effect of Gamma Irradiation on Structural and Optical Investigations of Borosilicate Glass Doped Yttrium Oxide

The structural, physical, and optical properties of prepared glass samples of the composition formula 30SiO₂-(40-x)B₂O₃-20Na₂O-10Al₂O₃-xY₂O₃, where x = 0, 1, 5, 7 (wt%) were studied before and after gamma irradiation using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-visible spectroscopy. The optical absorption spectra of study glasses were recorded in the UV/visible range of 200–900 nm. The optical band gap energies were calculated from absorption data. These results show that E_opt decreases with increasing concentration of Y₂O₃. The changes occurring in the optical parameters obtained from absorption spectra before and after irradiation have been referred to irradiation induced structural defects and compositional changes.