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1
Content available The MAS NMR study of solid solutions based on the YAG crystal
Padlyak B. V., Sergeev N. A., Olszewski M., Stępień P.
Nukleonika
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2015
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Vol. 60, No. 3, part 1
417--421
EN
An 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) study of nominally pure and Cr-doped yttrium-aluminum garnet (Y3Al5O12 and Y3Al5O12:Cr) crystals is reported. It has been shown that the doping by Cr of the Y3Al5O12 crystals leads to the variation of the occupation by Al atoms both octahedrally and tetrahedrally coordinated sites of the garnet lattice.
2
Content available remote Synthesis and optical spectroscopy of the lithium tetraborate glasses, doped with terbium and dysprosium
Padlyak B., Ryba-Romanowski W., Lisiecki R., Pieprzyk B., Drzewiecki A., Adamiv V., Burak Y., Teslyuk I.
Optica Applicata
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2012
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Vol. 42, nr 2
365-379
EN
A series of the Tb- and Dy-doped glasses with Li2O-2B2O3 (or Li2B4O7:Tb and Li2B4O7:Dy) composition were synthesised and their spectroscopic properties were investigated. The Li2B4O7:Tb and Li2B4O7:Dy glasses of high chemical purity and optical quality were obtained from corresponding polycrystalline compounds in the air using standard glass technology. The Tb and Dy impurities were added to Li2B4O7 composition in the form of Tb2O3 and Dy2O3 oxide compounds in amounts of 0.5 and 1.0 mol%. The electron paramagnetic resonance (EPR), luminescence excitation and emission spectra of the Li2B4O7:Tb and Li2B4O7:Dy glasses were investigated. On the basis of EPR and photoluminescence spectra analysis it was shown that the Tb and Dy impurities are incorporated in the Li2B4O7 glass network as Tb3+ (4f8, 7F6) and Dy3+ (4f9, 6H15/2) ions, exclusively. All observed transitions of the Tb3+ and Dy3+ centres in the luminescence excitation and emission spectra were identified. The luminescence kinetics shows single exponential decay for Tb3+ and Dy3+ centres in Li2B4O7 glasses. The lifetime values for main emission transitions of the Tb3+ and Dy3+ centres in the Li2B4O7 glasses containing 0.5 and 1.0 mol% Tb2O3 and Dy2O3 are determined at T = 300 K. Peculiarities of optical properties and local structure of the Tb3+ and Dy3+ centres in the Li2B4O7:Tb and Li2B4O7:Dy glasses as well as their potential applications have been discussed.
3
Content available Local structure and cohesive properties of mixed thorium and uranium dioxides calculated by "ab initio" method
Dąbrowski L., Szuta M.
Nukleonika
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2012
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Vol. 57, No. 1
101-107
EN
Density functional theory (DFT) results of calculations of the mixed thorium and uranium dioxide Th1-xUxO2 for the following mole ratio x = 0, 0.25, 0.75 and 1 are presented and discussed. "Ab initio" calculations were performed using the Wien2k program package. To compute the unit cell parameters the 12 atom super-cell were chosen. The lattice parameters were calculated through minimization of the total energy by the change of lattice parameters and atom displacement within the unit cell. Calculations were performed for five different exchange energy approximations EXC with and without corrective orbital potential U, and obtained lattice constants are presented graphically and compared with experimental data. It is established that the initially assumed oxygen location within the unit cell plus or minus 0.25 of the mixed compounds are not their equilibrium positions. The oxygen atoms within the unit cell undergo dislocation in the (111) direction. So, the distances oxygen-uranium are smaller than the distances oxygen-thorium. The change of local structure is presented graphically and appropriate parameters values are given in Table. The bulk modulus and the cohesive properties are also counted and shown graphically.
4
Content available remote Synthesis and optical spectroscopy of the Eu- and Pr-doped glasses with SrO–2B2O3 composition
Padlyak B., Grinberg M., Kuklinski B., Oseledchik Y., Smyrnov O., Kudryavtcev D., Prosvirnin A.
Optica Applicata
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2010
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Vol. 40, nr 2
413--426
EN
A series of Eu- and Pr-doped glasses with SrO–2B2O3 (or SrB4O7) composition were obtained and their spectroscopic properties were investigated. The SrB4O7 polycrystalline compounds were synthesised at T = 1300 K using high purity strontium carbonate (SrCO3) and boric acid (H3BO3). The Eu and Pr impurities were added to SrB4O7 compounds as Eu2O3 (amount: 0.167 at.%) and Pr2O3 (amounts: 0.05 and 0.25 at.%) oxides. The glass samples of high chemical purity and optical quality were obtained from corresponding polycrystalline compounds in the air atmosphere in platinum crucibles according to standard glass technology. Optical absorption, luminescence excitation and emission spectra of the Eu- and Pr-doped glasses with SrO–2B2O3 composition were investigated in the spectral range 300–800 nm at temperatures of 293 and 85 K. On the basis of optical spectra obtained and electron paramagnetic resonance (EPR) data analysis it is shown that Eu and Pr impurities are incorporated into the SrO–2B2O3 glass network as Eu3+ (4f6, 7F0) and Pr3+ (4f2, 3H4) ions, exclusively. All the observed transitions of the Eu3+ and Pr3+ centres in absorption and luminescence spectra were identified. The luminescence kinetics of Eu3+ and Pr3+ centres were investigated and analysed. The decay constants for main emission transitions in all samples investigated were obtained at room temperature. Peculiarities of incorporating the Eu3+ and Pr3+ activator ions in the glass with SrO–2B2O3 composition and their optical spectra are discussed in comparison with rare-earth doped polycrystalline compounds and single crystals with the same (SrB4O7) composition and other borate glasses.
5
Content available remote Optical spectra and luminescence kinetics of the Sm3+ and Yb3+ centres in the lithium tetraborate glasses
Padlyak B., Ryba-Romanowski W., Lisiecki R., Adamiv V., Burak Y., Teslyuk I., Banaszak-Piechowska A.
Optica Applicata
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2010
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Vol. 40, nr 2
427--438
EN
Optical absorption, luminescence excitation, and emission spectra as well as luminescence kinetics of the Sm- and Yb-doped glasses with lithium tetraborate (Li2B4O7) composition were investigated and analysed. The Sm- and Yb-doped lithium tetraborate glasses of high optical quality were obtained in air from corresponding polycrystalline compounds according to standard glass synthesis technology. The Sm and Yb impurities were added to the Li2B4O7 compound in the form of Sm2O3 and Yb2O3 oxides in amount of 0.4 mol%. Using optical and electron paramagnetic resonance spectroscopy it was shown that the Sm and Yb impurities are incorporated into the lithium tetraborate glass network as Sm3+ (4f5, 6H5/2) and Yb3+ (4f13, 2F7/2) ions, exclusively. All of the observed transitions in the absorption and luminescence spectra of Sm3+ and Yb3+ centres were identified. The luminescence kinetics of the Sm3+ and Yb3+ centres in the Li2B4O7 glass are characterised by a single exponential decay. Decay constants for the main emission transitions of the Sm3+ and Yb3+ centres in the lithium tetraborate glass were obtained at T = 300 K. Incorporation peculiarities and optical spectra of Sm3+ and Yb3+ ions in the lithium tetraborate glass have been discussed in comparison with other borate glasses and crystals.
6
Content available remote Optical spectroscopy and local structure of the Nd3+ luminescence centres in glasses of the CaO-Ga2O3-GeO2 system
Padlyak B., Ryba-Romanowski W., Lisiecki R.
Optica Applicata
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2008
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Vol. 38, nr 1
189-202
EN
Optical absorption and luminescence spectra as well as luminescence kinetics of the Nd3+ centres in glasses with Ca3Ga2Ge3O12:Nd composition, containing 0.2 and 1.0 wt% of the Nd2O3 were presented and analysed. The oscillator strengths and phenomenological intensity parameters omega t (omega 2, omega 4, and omega 6) were obtained using standard Judd-Ofelt theory. Calculated omega t parameters, radiative transitions rates, branching ratios and radiative lifetime for Nd3+ centres in the glass with Ca3Ga2Ge3O12 composition were analysed and compared with corresponding Nd3+ parameters in their crystalline analogue with garnet structure. Experimental lifetimes are compared with those calculated, and quantum efficiency of Nd3+ centres from 4F3/2 emitting level in the glass with Ca3Ga2Ge3O12 composition is estimated. Incorporation peculiarities and local structure of Nd3+ luminescence centres in the glass with Ca3Ga2Ge3O12 composition and corresponding Ca3Ga2Ge3O12:Nd3+ garnet laser crystals are considered. On the basis of extended X-ray absorption fine structure (EXAFS) spectra (L3-edge) of rare-earth elements analysis it has been shown that Nd3+ luminescence centres in the CaO-Ga2O3-GeO2 glass network occupy structural sites with the coordination number to oxygen N = 6.
7
Content available remote EXAFS/XANES studies of the local structure of amorphous ionic and electronic-ionic conductors
Wasiucionek M., Garbarczyk J., Bacewicz P., Jóźwiak J, Nowiński J.L.
Materials Science Poland
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2006
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Vol. 24, No. 1
181--186
EN
X-ray absorption spectroscopy methods such as EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-ray Absorption Near Edge Structure) are sophisticated and effective tools for studying the local structure of many solids and liquids. Their use is particularly valuable in the case of amorphous systems, in which due to the absence of long-range order the possibilities of structure determination by diffraction methods are limited. EXAFS and XANES have been extensively used to study the local structure of many electrically conducting (via ions, electrons, or both electrons and ions) solids. The special merit of the latter studies is that their results reveal the short-range structure of these conductors, which is an important factor determining their transport properties. The paper reports recent results of EXAFS/XANES studies on the local structure of selected electrically conducting glasses of the Li2O-V2O5-P2O5 system and their silver analogues. All spectra were acquired at the K-edge of vana
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