The high optical quality glasses with Li2B4O7:Eu, CaB4O7:Eu, and LiCaBO3:Eu compositions containing 0.5 and 1.0 mol. % Eu2O3 have been obtained by standard glass technology. Using electron paramagnetic resonance (EPR) and optical spectroscopy it was shown that the Eu impurity is incorporated into the Li2B4O7, CaB4O7, and LiCaBO3 glasses network as Eu3+ (4f6, 7F0) ions, exclusively. All observed f - f transitions of the Eu3+ centres in optical absorption, luminescence excitation and emission spectra were identified. Luminescence kinetic shows single exponential decay with different lifetimes for Eu3+ centres in the Li2B4O7, CaB4O7, and LiCaBO3 glasses.
The results of a comparative study of amorphous (Na, CO3)- and (K, CO3)-containing apatites by TPM MS analysis, FTIR, XRD, SEM and EPR are presented. Annealing of amorphous apatite at temperatures below 400°C does not lead to changing of nanoparticle shape and size and an extent of its crystallinity. A significant difference in the formation of γ-induced defects in (Na, CO3)- and (K,CO3)-containing apatites was found.
The Mg1-xZnxFe2O4 (x = 0, 0.2, 0.44, 0.5, 0.6) ferrite nanopowders of the spinel structure obtained by the sol-gel autocombustion (SGA) have been investigated using the X-ray diffraction and Mössbauer methods. The proofs were revealed verifying the potential occurrence of structural heterogeneity as solid solutions of various compositions of ferrites can be observed in a single phase system. In case of magnesium–zinc replacement, structural components occur, having different distribution of ferrum cations in crystallographic positions of the spinel lattice. The abnormal strength of nuclear effective fields is the indicator thereof. In addition, paramagnetic and superparamagnetic components were discovered there as well. This effect cannot be observed in the ferrite synthesis by the ceramic method.
High quality FexGa1-xBO3 single crystals with 0 ≤ x ≤ 1 were synthesized and studied by electron magnetic resonance in the temperature range from 4 to 290 K. At low x, only the electron spin resonance (ESR) of diluted Fe3+ ions is present. Fitting to the experimental ESR spectra, assuming distributions of Fe3+ ligand coordinates, has shown the existence of local disorder in the crystals.
The results of the effect of mechanical strain on magnetic anisotropy, the direction of magnetization vector and domain structure of ferrite-garnet film, rigidly connected with the zirconium-titanium lead (PZT) piezoceramic plate are presented. Since such a sandwich structure could be remagnetized both by magnetic field and electric voltage it could be used as the electro-magnetooptical modulator of light or spin switching cell in spintronics.
Selected optically stimulated luminescence properties of lithium aluminate crystals are presented within this work. Crystals were grown using Micro-Pulling-Down technique. The growth parameters and XRD analysis of obtained samples are demonstrated. OSL decay curves, thermal stability and fading of samples prepared under different conditions are compared.
The vitreous samples of MIxNa4-xCoFe(PO4)3 (x = 0, 0.2 and 1.0, MI - Li, K) composition were prepared by melt method. Formation of Nasicon-related crystalline samples was caused by the annealing at 600 °C. The cell parameters calculation showed that its evolution along two series agrees with the substitution of Na+ by smaller Li+ and bigger K+ cations. The electrical properties were investigated by the impedance method.
Behavior of light yield in wide range of inorganic scintillation crystals formed by isovalent substitution of anions or cations is summarized. The correlations between improvement of light yield in mixed crystals, and the ratios of ionic radii and atomic weights of the substituted atoms, as well as the bandgap difference between the components of mixed crystal, have been analyzed. It is presumed that non-monotonous dependence of light yield on components ratio in mixed scintillators is called by modulation of energy structure and limitation of carrier migration length due to spatial inhomogeneity in crystal. Phenomenological approach to prediction of light yield in mixed scintillation crystals has been proposed.
In this communication we analyze the reasons for distinctions of Yb 2+ → Yb 3+ recharging processes taking place in Yb:Y 3 Al 5 O 12 epitaxial films and bulk crystals under high temperature annealing. Influence of sample surface structure on the rate of oxidation process was found to be significant.
Samples of undoped yttrium and gadolinium tantalo-niobates with common formulae RE(NbxTa1-x)O4, where RE = Y or Gd, and x = 0-1, have been obtained by solid-state reaction. Optical and luminescent characteristics in visible and UV spectral regions have been studied. The most intense luminescence is determined for yttrium tantalo-niobates with intermediate value of Nb content in the matrix and for heavy Nb - doped gadolinium tantalo-niobates.
The purpose of this work is to study the possibility to improve light collection in conditions similar to than in cryogenic scintillating bolometers. Energy resolution and relative pulse amplitude of scintillation detectors were measured using CaWO4 crystals with different shapes (cylindrical. hexagonal and cube prism). reflector materials and shapes. optical contact and surface conditions (polished and diffused). Light collection was simulated using ZEMAX codes.
The polycrystalline samples of K 2 BiZr(PO 4 ) 3 were synthesized by spontaneous crystallization method. The photoluminescence (PL) spectroscopy studies of K 2 BiZr(PO 4 ) 3 are carried out under the VUV synchrotron excitations. The electronic structure of K 2 BiZr(PO 4 ) 3 is calculated by the FLAPW method. The PL spectra of K 2 BiZr(PO 4 ) 3 reveal two main components in the UV and visible spectral regions (peaking near 3.6 and 2.6 eV respectively). It is assumed that the UV PL component of K 2 BiZr(PO 4 ) 3 originates from transitions in ZrO 6 polyhedra, while the visible one is related to Bi 3+ ions in oxygen coordination.
The new method of the nanoparticle log-normal distribution parameters determination for superparamagnetic nanoparticle system of core-shell type is proposed. It is based on measurements of the nonlinear magnetic susceptibility and is compared with other commonly used techniques.
The Reference Book of ternary systems phase diagrams computer models for molybdenum and tungsten compounds is presented. Its models give a possibility to calculate the mass balances in any temperature intervals, to observe crystallization history and the process of microstructure forming at different crystallization stages.
The La1-xEuxVO4 powders were synthesized by co-precipitation method. Luminescence spectra of the investigated samples consist of wide non-structural bands of the matrix emission and narrow spectral lines caused by inner f-f electron transitions in the impurity Eu3+ ions. The both types of emission were studied within 10 - 300 K temperature range. Obtained dependencies are discussed using proposed models for matrix emission and structure of the nearest surrounding of the Eu3+ centers.
The photoluminescence properties of undoped Al(PO3)3 crystals synthesized by flux method are studied under VUV synchrotron excitations. The electronic structure of Al(PO3)3 crystals is calculated by the FLAPW method. The PL emission spectra of Al(PO3)3 reveal emission bands in the violet and in the yellow-red spectral regions. Obtained results point to an active role of the electronic states of phosphate groups in the processes of intrinsic luminescence in Al(PO3)3 crystals.
The series of V-doped glasses with Li2O-2B2O3 (Li2B4O7), 1/2(Li2O-K2O-4B2O3), (LiKB4O7), CaO-2B2O3 (CaB4O7) and 1/2(Li2O-2CaO-B2O3) (LiCaBO3) composition containing 0.5 and 1.0 mol. % V2O5 oxide were obtained by standard glass technology. The electron paramagnetic resonance (EPR) and optical absorption spectra of the obtained glasses were investigated at T = 300 K. The spin Hamiltonian parameters for observed EPR spectra in the Li2B4O7:V, LiKB4O7:V, CaB4O7:V and LiCaBO3:V glasses were determined and electron and local structure of impurity V centres were proposed. The optical absorption bands, observed in the investigated glasses have been interpreted.
The investigation of concentration fields of T-x-y diagram is considered by use of its computer model. Phase diagram of CaO-SiO2-Al2O3 system is used as an example.
Experimental and theoretical results about contribution of molecular anionic (MA) groups into luminescence of ion-covalent, in other words, HeteroDesmic Crystals (HDC,) are presented in this work. Obtained results are discussed using many published data and previously performed studies at R&D Lab. “Condensed Matter Spectroscopy (COMS)” of Kyiv National Taras Shevchenko University.
