Laser-induced anisotropy in Ag<Superscript>+</Superscript>-doped glasses

An induced optical anisotropy is observed as a result of interaction of a high-power CW Ar⁺ laser beam, with silver-ion-exchanged glasses. We have shown that the absorption of the beam by the thin layer of Ag⁺ produces a temperature gradient resulting in a radial stress on the surface of the sample. The induced anisotropy makes the sample behave as a thin uniaxial optical medium with axis along the direction of the beam propagation. For the polarized light, the induced anisotropy restricts the application of micro-lenses, which are made by this method. The average refraction index of the interaction area is measured.     

NIR-excited NIR and visible luminescent properties of amphipathic YVO<Subscript>4</Subscript>: Er<Superscript>3+</Superscript>/Yb<Superscript>3+</Superscript> nanoparticles

This article reports the luminescence properties of amphipathic YVO₄:Er³⁺/Yb³⁺ nanoparticles (average grain size ca. 20 nm) obtained by an oleate-aided hydrothermal process. Depending on the upconversion (UPC) and downconversion (DWC) processes, they show luminescence in the visible and near-infrared (NIR) regions, respectively, by 980-nm excitation. The sample doped with Er³⁺:2.5 mol% and Yb³⁺:10 mol% showed the highest luminescence intensity in both the visible and NIR regions as a result of efficient energy transfer from Yb³⁺ to Er³⁺ ions. The hydrothermal treatment greatly enhanced both the DWC and UPC luminescence efficiencies. This is due to the reduction in the concentration of surface defects and ligands, accompanied by grain growth. NIR Fluorescence microscopy revealed for the first time that DWC luminescence is sufficiently intense for application of these nanocrystals as a NIR bioprobe.     

Studies of Fe-doped SiO<Superscript>2</Superscript>/TiO<Superscript>2</Superscript> composite nanoparticles prepared by sol-gel-hydrothermal method

Fe-doped SiO²/TiO² composite nanoparticles were directly prepared by sol-gel-hydrothermal process, and characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), thermal gravimetry (TG), X-Ray photoelectron spectroscopy (XPS), and UV-Vis diffuse reflectance spectra (DRS). It was found that the Fe^{3 +} was well dispersed in solid solution of SiO²/TiO² composite nanoparticles that was about 10 nm with spherical morphology and rich silica layer external surface. It could effectively offer broadband shield for both UVB (290–320 nm) and UVA (320–400 nm). The results of Photodecomposition of methylene blue showed that the photoactivity of Fe-doped SiO²/TiO² composite was minimized due to the addition of iron ion.     

Electrical Conductivity of Bi<Subscript>2</Subscript>WO<Subscript>6</Subscript> Crystals Doped with Ca<Superscript>2+</Superscript>, Pb<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript>, and Ba<Superscript>2+</Superscript>

Single crystals of Bi₂WO₆ (a layered perovskite-like compound) doped with Ca²⁺, Pb²⁺, Sr²⁺, and Ba²⁺ on the Bi³⁺ site are grown, and their oxygen ionic conductivity is measured along the polar axis. The intrinsic conductivity of the doped crystals differs insignificantly from the conductivity of undoped Bi₂WO₆, indicating that the oxygen ions in the Bi₂O₂ layers contribute little to the oxygen ionic conductivity of the crystals. The sharp change in the activation energy for conduction at 600°C attests to a transition from one conduction mechanism to another in going from low to high temperatures.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 7, 2005, pp. 863–865.Original Russian Text Copyright © 2005 by Kharitonova, Voronkova, Yanovskii.     

Isolation of <Superscript>58</Superscript>Co, <Superscript>54</Superscript>Mn,and <Superscript>86</Superscript>Rb from <Superscript>89</Superscript>Sr production wastes

Procedures for isolation of ⁵⁸Co, ⁵⁴Mn, and ⁸⁶Rb from ⁸⁹Sr production wastes are described. The production of ⁸⁹Sr was based on irradiation of natural Y in the form of oxide, placed in 1Cr18Ni10Ti stainless steel ampules, on a BR-10 fast reactor. ⁵⁸Co and ⁵⁴Mn were isolated from the casings of stainless steel ampules, and ⁸⁶Rb, from the tail solution after the isolation of ⁸⁹Sr.     

Influence of microstructure on the luminescence properties of YVO<Subscript>4</Subscript>:Eu<Superscript>3+</Superscript> nanoparticles

YVO₄:Eu³⁺ nanoparticles were synthesized by hydrothermal method at different conditions. The microstructures and photoluminescence (PL) properties of the as-prepared YVO₄:Eu³⁺ nanoparticles were investigated by X-ray powder diffraction, field emission scanning electron microscopy and PL spectroscopy. The detailed relationship between the microstructures and luminescence properties was investigated. It has been found that the crystallinity, the grain size and the duty factor of Eu³⁺ play important roles in influencing the luminescence properties. The article is published in the original.     

Organic additive assisted hydrothermal synthesis and photoluminescence properties of CeF<Subscript>3</Subscript>:Tb<Superscript>3+</Superscript> and NaCeF<Subscript>4</Subscript>:Tb<Superscript>3+</Superscript> nanoparticles

A series of Tb³⁺ doped CeF₃ and NaCeF₄ nanoparticles with different morphology and dimension were synthesized via hydrothermal method. Different organic additives, including sodium dodecyl sulfonate (SDS), polyvinylpyrrolidone (PVP), cetyltrimethyl ammonium bromide (CTAB), oleic acid (OA), polyethylene glycol (PEG), trisodium citrate (Cit) were introduced to control the crystallite size and morphology. Powder X-ray diffraction (PXRD), fourier transform infra-red spectra (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and down-conversion (DC) photoluminescence spectra were used to characterize the samples. The emission peaks of all the prepared samples centered at 490, 545, 585 and 621 nm which can be ascribed to the ⁵D₄→⁷F_J (J?=?6, 5, 4, 3) transitions respectively of Tb³⁺ ion. However, emission intensities are strongly controlled by morphology and particle sizes which are influenced by different organic additives used in synthesis. Moreover, the crystal growth process was monitored through a series of time-dependent experiments and a possible formation mechanism has been proposed.     

High-purity silicon isotopes <Superscript>28</Superscript>Si, <Superscript>29</Superscript>Si,and <Superscript>30</Superscript>Si

The current status of the problem of obtaining high-purity silicon isotopes ²⁸Si, ²⁹Si, and ³⁰Si is analyzed. The scheme of obtaining monoisotopic silicon includes the stages of isotope separation in the form SiF₄, synthesis and deep purification of isotopically enriched silane, obtaining polycrystalline silicon-28,-29, and-30, and growing monocrystals. The basic problems and methods of their solution in the synthesis and deep purification of silane and obtaining poly-and monocrystals of isotopically enriched silicon are discussed. Data characterizing the achieved level of chemical and isotopic purity of high-purity monocrystals of silicon-28 with a main isotope content of more than 99.99% and silicon-29 and silicon-30 with isotopic purity higher than 99% are presented. In monocrystalline ²⁸Si, the boron content was 4.5 × 10¹³, the phosphorus content was 5 × 10¹¹, the carbon and oxygen contents were <1 × 10¹⁶ at/cm³, and the specific resistance was 800 Ω cm. The results of investigation of heat capacity, heat conduction, photoluminescence, and electron paramagnetic resonance spectra for monoisotopic silicon-28 are presented. The heat conduction of monoisotopic silicon is increased considerably owing to the reduced photon scattering on isotopic inhomogeneities. In the region of 20–30 K, the heat conduction of silicon-28 with an isotopic purity of 99.98% is higher by a factor of 8 than the heat conduction of natural silicon. Investigations of photoluminescence spectra in the magnetic field in the low-temperature region demonstrated the capability of optical detection of nuclear spin states of a phosphorus admixture in high-purity silicon-28. p ]Topical questions for further investigations and possible fields of practical application of high-purity isotopically enriched silicon are discussed.     

Synthesis and properties of laser-active liquids POCl<Subscript>3</Subscript>-SbCl<Subscript>5</Subscript>-<Superscript>235</Superscript>UO<Stack><Subscript>2</Subscript><Superscript>2+</Superscript></Stack>-Nd<Superscript>3+</Superscript>

The effect of the synthesis conditions on the properties of inorganic laser-active liquids POCl₃-SbCl₅-²³⁵UO ₂ ²⁺ -Nd³⁺ is considered. The kinetic dependences of the U(IV) content and decay time of the Nd³⁺ luminescence in POCl₃-SbCl₅-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions for various synthesis procedures at 380 K have been obtained. In POCl₃-SbCl₅-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions, nonradiative energy transfer Nd³⁺ → U⁴⁺ is observed, and quenching of the Nd³⁺ luminescence is described by the Stern-Volmer law: k _q = (6.4 ± 0.6) × 10⁵ l mol^?1 s^?1. Laser liquids POCl₃-SbCl₅-²³⁵UO ₂ ²⁺ -Nd³⁺ with neodymium concentration of up to 0.7 M, uranyl concentration of up to 0.1 M, and decay time of the Nd³⁺ luminescence of up to 220 μs have been prepared for the first time.     

Electrical and physicochemical properties of some Ag<Subscript>2</Subscript>O-containing lithia iron silica phosphate glasses

The present paper reports the influence of Ag₂O addition at the expense of Li₂O on the local structure of xAg₂O·(30 − x)Li₂O·10Fe₂O₃·10SiO₂·50P₂O₅ glass matrix (with x = 0, 0.5, 1, 1.5 and 2 mol %). The phosphate structural units of the network former are assessed from Fourier transform infrared (FT-IR) spectroscopy. The addition of Ag₂O to the glass network matrix ≤1 mol % leads to the occurrence of a depolymerization process of the phosphate structure and consequently, to the appearance of a distortion of the PO₄ tetrahedra. When the content of Ag₂O is increased from 1.5 up to 2 mol %, a remarkable polymerization process has been observed. The density, molar volume, microhardness and chemical durability have been investigated in order to study the effect of Ag₂O/Li₂O replacements on the physicochemical properties the studied glasses. The AC electrical properties are affected to a great extent with composition. These results are related to the internal structure of the glass samples. The conductivity, dielectric constant and dielectric loss of the studied glasses were studied using the frequency response in the interval 100 Hz–100 kHz and the effect of compositional changes on the measured properties was investigated. Measurements showed that the electrical responses of glass samples were different and complex for interpretation. The increase of Ag₂O addition at the expense of Li₂O contents (from 0 to 1 mol %) led to increase the conductivity, dielectric constant and dielectric losses of samples. The addition of more Ag₂O at the expense of Li₂O (from 1.5 to 2 mol %), resulting into decreasing the conductivity, the dielectric constant and dielectric losses of the studied glasses. The experimental data of the glass samples were argued to the internal structure of the glasses and the nature and role-played by weakening or increasing the rigidity of the structure of the sample. It could be concluded, therefore, that the AC electrical properties of the samples were influenced by the distribution of its constituents, connectivity, and number of free charges.     

Sn<Superscript>4+</Superscript> and La<Superscript>3+</Superscript> co doped TiO<Subscript>2</Subscript> nanoparticles and their optical,photocatalytic and antibacterial properties under visible light

Sn⁴⁺ and La³⁺ co-doped TiO₂ photocatalytic material with nanoparticle structure have been successfully prepared using SnCl₂·2H₂O and La(NO₃)₃·6H₂O as precursors. Scanning electron microscopy, X-ray diffraction, transmission electron microscopy and UV–visible spectroscopy have been used to for the characterization of the morphology, crystal structure, particle size and optical properties of the samples. The photocatalytic properties of sample with various amount of La doped TiO₂ have been studied by photo degradation of methyl orange (MO) in water under visible light. XRD patterns showed both rutile and anatase phases for 5 mol% of Sn and 5–10 mol% of La. But anatase phase with a little rutile phase was formed for 5 mol%Sn and 10 mol%La. The prepared Sn and La co doped TiO₂ photo-catalyst showed optical absorption edge in the visible light area and exhibited excellent photo-catalytic ability for degradation of MO solution under visible irradiation. Antibacterial behavior towards E. coli was then studied under visible irradiation. The synthesized T-5%Sn-10%La powder exhibited superior antibacterial activity under visible irradiation compared to the pure TiO₂.     

Morphology and luminescent properties of Al<Superscript>3+</Superscript>/Mg<Superscript>2+</Superscript>-doped Y<Subscript>2</Subscript>O<Subscript>3</Subscript>:Eu<Superscript>3+</Superscript> phosphor

Al³⁺/Mg²⁺ doped Y₂O₃:Eu phosphor was synthesized by the glycine-nitrate solution combustion method. In contrast to Y₂O₃:Eu which showed an irregular shape of agglomerated particles (the mean particle size >10 μm), the morphology of Al³⁺/Mg²⁺ doped Y₂O₃:Eu crystals was quite regular. Al³⁺/Mg²⁺ substituting Y³⁺ in Y₂O₃:Eu resulted in an obvious decrease of the particle size. Meanwhile, higher the Al³⁺/Mg²⁺ concentration, smaller the particle size. In particular, the introduction of Al³⁺ ion into Y₂O₃ lattice induced a remarkable increase of PL and CL intensity. While, for Mg²⁺ doped Y₂O₃:Eu samples, their PL and CL intensities decreased. The reason that causes the variation of PL and CL properties for Al³⁺ and Mg²⁺ doped Y₂O₃:Eu crystals was concluded to be related to sites of Al³⁺ and Mg²⁺ ions inclined to take and the difference of ion charge.     

Behavior of Microamounts of <Superscript>22</Superscript>Na, <Superscript>85</Superscript>Sr, <Superscript>137</Superscript>Cs,and <Superscript>152</Superscript>Eu in Sorption and Coprecipitation on Mixed Potassium Neodymium Ferrocyanide from Solutions

Sorption of ⁸⁵Sr, ¹³⁷Cs, ²²Na, and ¹⁵²Eu on solid mixed potassium neodymium ferrocyanide KNd[Fe(CN)₆]·4H₂O from neutral, acidic, and alkaline media and also coprecipitation of these radionuclides with KNd[Fe(CN)₆]·4H₂O in its formation from a homogeneous solution were studied. It was found that ⁸⁵Sr and ²²Na do not noticeably coprecipitate with solid KNd[Fe(CN)₆]·4H₂O and are not sorbed by this substance. In aqueous medium, depending on the cesium concentration in solution, from 80 to 98% of ¹³⁷Cs coprecipitates with solid KNd[Fe(CN)₆]·4H₂O. In this case, the distribution coefficient K_d depends on both the cesium concentration in solution and solution pH. Within 30 min of contact of the solid and liquid phases, the degree of recovery of ¹³⁷Cs from aqueous solution with KNd[Fe(CN)₆]·4H₂O is approximately 95.0% of the initial amount. ¹⁵²Eu coprecipitates with solid KNd[Fe(CN)₆]·4H₂O during its formation from a homogeneous solution to 98–99.9%. The degree of recovery of ¹⁵²Eu from aqueous solution with KNd[Fe(CN)₆]·4H₂O precipitate within 60 min of contact of the solid and liquid phases is 70.3% of the initial amount.     

Fine purification of monoisotopic <Superscript>32</Superscript>S and <Superscript>34</Superscript>S

We have proposed and tested a combined process for ultrapurification of monoisotopic ³²S and ³⁴S sulfur, which comprises thermochemical treatment of sulfur vapor on silica and ceria packing, melting with aluminum, and distillation. The impurity composition of the purified sulfur has been determined by atomic emission and IR spectroscopy. We have obtained monoisotopic ³²S and ³⁴S sulfur samples comparable in chemical purity to high-purity sulfur of natural isotopic composition.     

Distribution of <Superscript>137</Superscript>Cs, <Superscript>90</Superscript>Sr, <Superscript>239 + 240</Superscript>Pu, <Superscript>241</Superscript>Am,and <Superscript>244</Superscript>Cm among Components of Organic Matter of Soils in Near Exclusion Zone of the Chernobyl NPP

Distribution of Chernobyl-derived ¹³⁷Cs, ⁹⁰Sr, ^{239 + 240}Pu, ²⁴¹Am, and ²⁴⁴Cm among organic fractions of soddy-podzolic, sandy, soddy-meadow, and peat soils collected from the Chernobyl Exclusion Zone along the North-Western radioactive fallout track was determined. Regardless of the soil type, 80–85% of ¹³⁷Cs is tightly fixed on the mineral fraction of the soil. Depending on the soil type, 50–70% of ⁹⁰Sr and 15– 45% of ²⁴¹Am are associated with fulvic acid fractions. ²⁴¹Am and ²⁴⁴Cu are similarly distributed among the organic acid fractions. In all the soil types studied, ^{239 + 240}Pu is associated essentially with humic acid fractions. Natural ^{230, 232}Th and technogenic ^{239 + 240}Pu are similarly distributed among the organic fractions.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 91–96.Original Russian Text Copyright © 2005 by Odintsov, Pazukhin, Sazhenyuk.     

Luminescent properties of Pb<Superscript>2+</Superscript>- and Mn<Superscript>2+</Superscript>-activated CdI<Subscript>2</Subscript> crystals

The luminescent properties of CdI₂, CdI₂:Pb²⁺, CdI₂:Mn²⁺, and CdI₂:Pb²⁺,Mn²⁺) crystals have been studied at temperatures from 85 to 295 K under optical and x-ray excitation. Analysis of new and earlier spectroscopic data suggests that the 560-nm luminescence of CdI₂:Pb²⁺ and CdI₂:(Pb²⁺,Mn²⁺) crystals under excitation on the long-wavelength component of the A absorption band of Pb²⁺ centers is due to Pb²⁺-bound anion excitons. The 640-to 660-nm emission of these crystals is attributable to α centers. The manganese luminescence in the codoped material originates from both intracenter Mn²⁺ excitations and a sensitized process due to energy transfer from the host and Pb²⁺-related centers. The mechanisms of recombination and energy transfer processes in cadmium iodide crystals codoped with Pb²⁺ and Mn²⁺ are discussed.     

Void formation and cracking of Zr<Superscript>41</Superscript>Ti<Superscript>14</Superscript>Cu<Superscript>12.5</Superscript>- Ni<Superscript>10</Superscript>Be<Superscript>22.5</Superscript> bulk metallic glass under planar shock compression

Planar shock compression effects on void formation and cracking in Zr⁴¹Ti¹⁴Cu^12.5Ni¹⁰Be^22.5 bulk metallic glass (BMG) are studied in this paper. Cracking was found to be a result of void linkage in some direction deviation from the maximum shear stress plane. Changing the state of the stress inside the BMG sample led to formation of different void distribution. Nucleation of the microvoids was possibly initiated by release of excess free volume under shock wave compression.     

Synthesis and properties of AgTi<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>-based NASICON-type phosphates doped with Nb<Superscript>5+</Superscript>, Zr<Superscript>4+</Superscript>, and Ga<Superscript>3+</Superscript>

We have synthesized materials based on a silver titanium phosphate with partial substitution of tri-, tetra-, or pentavalent cations for titanium: Ag_1±x Ti_2−x M _x (PO₄)₃ (M = Nb⁵⁺, Ga³⁺) and AgTi_2−x Zr _x (PO₄)₃. The materials have been characterized by X-ray diffraction and impedance spectroscopy and have been shown to have small thermal expansion coefficients. Their ionic conductivity has been determined. Silver ions in these materials are difficult to replace with protons.     

Phase stabilization and structural studies of nanocrystalline La<Superscript>2</Superscript>O<Superscript>3</Superscript>-ZrO<Superscript>2</Superscript>

La²O³ doped nanocrystalline zirconia (ZrO²) has been prepared by chemical co-precipitation method for various dopant concentrations, varying from 3 to 30 mol%. Structural phases have been characterized by X-ray diffraction technique. All the as-synthesized samples were found to be in monoclinic phase. Annealing of the samples at different temperatures from 400 to 1000∘C stabilized ZrO² either partially or fully the tetragonal/cubic phases. When they were annealed at 1200∘C, the monoclinic phase appeared again with a new cubic pyrochlore structured La²Zr²O⁷ at the expense of stabilized tetragonal phase. Formability of the tetragonal/cubic phase has been influenced by the dopant concentration and the annealing temperature. Sample with 8 mol% La²O³ has been stabilized completely in tetragonal/cubic phase after annealing at 900∘C for 1 h. Smallness of the grain in these nanocrystalline materials may also have assisted in the formation of La²O³-ZrO² solid solution.     

Complexation of polyethylene glycol with Sr<Superscript>2+</Superscript> and Ba<Superscript>2+</Superscript> cations in extracts containing chlorinated cobalt dicarbollide

The composition and structure of complexes that are formed in the system consisting of chlorinated cobalt dicarbollide (CCD), polyethylene glycol (PEG), and Sr²⁺ or Ba²⁺ in a polar diluent, dichloroethane or phenyl trifluoromethyl sulfone, were studied by IR and NMR spectroscopy. In extraction of Sr²⁺ and Ba²⁺ with solutions of [H₅O ₂ ⁺ PEG]CCD^–, the organic phase contains the ionic associates [M²⁺PEG]CCD ₂ ^– . The Sr²⁺ and Ba²⁺ complexes have similar composition and structure: The oxygen atoms of two OH groups and six COC groups of a PEG molecule fill the first coordination sphere of the metal ions. Also, no more than two water molecules can be coordinated in the second sphere, forming hydrogen bonds with the hydrogen atoms of two OH groups of PEG. The coordination of the OH groups of PEG with the Sr²⁺ and Ba²⁺ ions is preferable over the coordination of the COC groups, as follows from the fact that the extraction of Sr²⁺ and Ba²⁺ with CCD-PEG mixtures gets worse on replacement of the OH groups of PEG by other substituents. A considerable increase in the efficiency of Sr²⁺ and Ba²⁺ extraction with H-CCD solutions in the presence of PEG is due to the fact that all the H₂O molecules in the first coordination spheres of the M²⁺ ions are replaced by the COC and OH groups of PEG with the formation of a hydrophobic complex [M²⁺PEG](H₂O)₂.Translated from Radiokhimiya, Vol. 46, No. 6, 2004, pp. 540–545.Original Russian Text Copyright © 2004 by Stoyanov, Smirnov, Babain, Antonov, Peterman, Herbst, Todd, Luther.