Origin of supercoolability in metallic and halide melts is discussed. While the level of supercooling in metals is closely connected with the structural incompatibilities between the molten state and product crystal, respectively, the... more
Origin of supercoolability in metallic and halide melts is discussed. While the level of supercooling in metals is closely connected with the structural incompatibilities between the molten state and product crystal, respectively, the supercoolability of halide melts is caused by their strong complexforming nature. The investigation of processes in supercooled melts is important, because the supercooling of melt strongly influences the nucleation and growth of crystals from the melt and their final quality. Electrical resistance is a suitable quantity to study the solidification of melts, since it can be measured both in liquid state (including supercooled melt) and during the solidification. The early stage of solidification of PbBr 2 melt was analyzed within the context of nonstationary nucleation theory. The proposed model describes the time dependence of electrical conductivity of the melt. The time lag of nucleation is calculated and compared with the experimental value.
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We report on spectroscopic investigations of Nd{sup 3+}- and Tb{sup 3+}- doped low phonon energy, moisture-resistant host crystals, KPbBr and RbPbBr, and their potential to serve as new solid state laser materials at new wavelengths,... more
We report on spectroscopic investigations of Nd{sup 3+}- and Tb{sup 3+}- doped low phonon energy, moisture-resistant host crystals, KPbBr and RbPbBr, and their potential to serve as new solid state laser materials at new wavelengths, especially in the long wavelength infrared region. This includes emission spectra, emission lifetime measurements, Raman scattering spectra as well as calculations of the multiphonon decay
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We present a model allowing to estimate the so-called time lag of nucleating halide melts using electrical conductivity measurements. Due to the complex-forming nature of molten halide salts we suppose two basic types of charge carriers... more
We present a model allowing to estimate the so-called time lag of nucleating halide melts using electrical conductivity measurements. Due to the complex-forming nature of molten halide salts we suppose two basic types of charge carriers in the melt: complexes (playing the role of monomers-building units) and clusters of a newly forming solid phase. Within context of the nonstationary nucleation theory we determined a formula expressing the time dependency of electrical conductivity of such a system and compared this result with the experimental data obtained for the melts of PbBr2, PbCl2, and KPb2Cl5. In terms of this formula the time lag of nucleation may be estimated. This important quantity characterizing the moment from which the nucleated clusters only grow to the macroscopic sizes has been found to be approximately 75% of the total duration of the nucleation process itself.
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The structure and optical properties of thin films grown by the vacuum co-evaporation of CsI and PbI2 powders from two independent crucibles were studied. The typical thickness of the films grown was approximately 0.5 μm. X-Ray... more
The structure and optical properties of thin films grown by the vacuum co-evaporation of CsI and PbI2 powders from two independent crucibles were studied. The typical thickness of the films grown was approximately 0.5 μm. X-Ray diffraction spectroscopy using different grazing angles (0.1°–2°) revealed formation of ternary phases, namely CsPbI3 and Cs4PbI6 ones in the thin film samples and gave
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The optical transparency of PbWO 4 single crystals in the short wavelength region between 320 nm (cutoff) and 450 nm is significantly improved by doping with a small amount of La. This result indicates the possibility that the light yield... more
The optical transparency of PbWO 4 single crystals in the short wavelength region between 320 nm (cutoff) and 450 nm is significantly improved by doping with a small amount of La. This result indicates the possibility that the light yield detected by photomultipliers in actual detectors ...
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ABSTRACT Present characteristics of scintillating properties of rare earth aluminum garnets RE3Al5O12, where RE are Lu, Y or their mixture in asked ratio, doped with Ce3+ or Pr3+ are presented. The highest light yield up to 27000 ph/MeV... more
ABSTRACT Present characteristics of scintillating properties of rare earth aluminum garnets RE3Al5O12, where RE are Lu, Y or their mixture in asked ratio, doped with Ce3+ or Pr3+ are presented. The highest light yield up to 27000 ph/MeV was observed on LuAG:Ce crystals (CZ grown) while that observed on LuAG:Pr can reach ∼17000 ph/MeV at 10 μs shaping time. Mixed (Lu, Y)AG crystals can reach ∼23500 ph/MeV (Ce3+ doped ones) or ∼16500 ph/MeV (Pr3+ doped ones). The latest development in LPE grown Ce3+ or Pr3+ doped epitaxial garnet layers has shown that their photoelectron yields are comparable with that of the best Ce3+ or Pr3+ doped crystals. Light yields of LuAG:Ce or LuAG:Pr crystals can increase due to annealing in air up to 20 or 29%, respectively.
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The behavior of an octahedral center created in alkali chloride and bromide single crystals by doping with divalent lead is analyzed using the experimental results from absorption and luminescence measurements. We focus on the questions... more
The behavior of an octahedral center created in alkali chloride and bromide single crystals by doping with divalent lead is analyzed using the experimental results from absorption and luminescence measurements. We focus on the questions of local distortion both in ground and excited states, the regularities in A(T) and A(x) emissions and differences in the decay shape of high energy emission.
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ABSTRACT Emission and absorption properties of RbPb2Cl5 crystals are reported for the first time at the temperature 4.2 to 300 K. The lowest energy absorption peak at 275 nm is ascribed to a cationic exciton at Pb2+ site analogically to... more
ABSTRACT Emission and absorption properties of RbPb2Cl5 crystals are reported for the first time at the temperature 4.2 to 300 K. The lowest energy absorption peak at 275 nm is ascribed to a cationic exciton at Pb2+ site analogically to PbCl2. Two emission bands are found peaking at 340 and 510 nm under excitation in the exciton absorption region. They are ascribed to radiative decay of the cationic exciton at two different minima of excited APES at the Pb2+ ion. A comparison of RbPb2Cl5 emission properties with those of PbCl2 and RbCl:Pb is made.Erstmalig werden die Absorptions- und Emissionseigenschaften von RbPb2Cl5-Kristallen bei Temperaturen von 4,2 bis 300 K publiziert. Das Absorptionsmaximum bei 275 nm wird dem Kation-Exziton am Pb2+-Platz zugeordnet, ähnlich wie im Fall des PbCl2-Kristalls. Zwei Lumineszenzbanden bei 340 und 510 nm werden unter Anregung im Exzitonenabsorptionsbereich festgestellt. Sie werden dem strahlenden Übergang des Kation-Exzitons bei zwei verschiedenen Anregungzustandminima der Pb2+-Ionen zugeordnet. Die Emissionseigenschaften der RbPb2Cl5, PbCl2, und RbCl:Pb-Kristalle werden verglichen.
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Single crystals of PbW04 (PWO) are intensively studied in the last few years in connection with their potential application for scintillation detectors in high energy physics [I, 21. Within the last year a dramatic increase of this... more
Single crystals of PbW04 (PWO) are intensively studied in the last few years in connection with their potential application for scintillation detectors in high energy physics [I, 21. Within the last year a dramatic increase of this research activity has been observed [3] in ...
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Effect of cation substitutions on the nuclear magnetic relaxation of 57Fe was measured in epitaxial films of Y3Fe5−xAlxO12 (x=0.004–0.17), Y3Fe5−xInxO12 (0.002–0.24) and Y3−xLaxFe5O12 (0.001–0.04). Measurements were carried out in zero... more
Effect of cation substitutions on the nuclear magnetic relaxation of 57Fe was measured in epitaxial films of Y3Fe5−xAlxO12 (x=0.004–0.17), Y3Fe5−xInxO12 (0.002–0.24) and Y3−xLaxFe5O12 (0.001–0.04). Measurements were carried out in zero external magnetic field at 4.2K. Decrease of the spin–lattice and the spin–spin (except for the In substitutions above x∼0.05) relaxation rates with increased concentration was found.
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Luminescence of CsPbX3-like quantum dots in CsX crystal host (X = Cl, Br) is reported. Single band spectrum is found for as grown or heavily annealed (T = 240 °C) CsX:Pb, while a family of emisssion bands is observed after annealing at... more
Luminescence of CsPbX3-like quantum dots in CsX crystal host (X = Cl, Br) is reported. Single band spectrum is found for as grown or heavily annealed (T = 240 °C) CsX:Pb, while a family of emisssion bands is observed after annealing at temperatures below 210 °C. Anisotropie growth of quantum dots in the early stage is proposed and positions of
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ABSTRACT The emission and the decay kinetics under one- and two-photon excitation were measured for a CsPbCl3 single crystal. Three emission processes were identified in the emission spectrum and their temperature dependencies were... more
ABSTRACT The emission and the decay kinetics under one- and two-photon excitation were measured for a CsPbCl3 single crystal. Three emission processes were identified in the emission spectrum and their temperature dependencies were approximated by a simple model under 80 K. Two components were found in the luminescence decay in the subnanosecond and nanosecond time scales.
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X-ray-excited luminescence and time-resolved UV-excited photoluminescence were employed to evidence energy transfer processes between two main emission components in PbWO4 scintillating single crystals. It was found that energy transfer... more
X-ray-excited luminescence and time-resolved UV-excited photoluminescence were employed to evidence energy transfer processes between two main emission components in PbWO4 scintillating single crystals. It was found that energy transfer from the blue to green emission centres occurs via free-charge carriers above 150 K. This process causes a redistribution of the emitted energy in favour of the green emission component. At
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Lead halides (PbCl2, PbBr2 and PbI2) of various sources were examined by the DTA method in order to analyse polymorphism in these compounds. Only one peak corresponding to melting was found in the DTA curves of high-purity lead halides.... more
Lead halides (PbCl2, PbBr2 and PbI2) of various sources were examined by the DTA method in order to analyse polymorphism in these compounds. Only one peak corresponding to melting was found in the DTA curves of high-purity lead halides. This confirms that there is no phase transition in lead halides between room temperature and their melting point and therefore previous
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Photo- and radioluminescence, decay kinetics, and thermoluminescence are reported for a set of Ce3+-doped phosphate glasses. The presence of Gd3+ ions in the glass host matrix at concentrations above 20% enhances the energy transfer... more
Photo- and radioluminescence, decay kinetics, and thermoluminescence are reported for a set of Ce3+-doped phosphate glasses. The presence of Gd3+ ions in the glass host matrix at concentrations above 20% enhances the energy transfer towards the Ce3+ emission centers, which results in a remarkable enhancement of the radioluminescence light output.