Origin of supercoolability in metallic and halide melts is discussed. While the level of supercoo... 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.
We report on spectroscopic investigations of Nd{sup 3+}- and Tb{sup 3+}- doped low phonon energy,... 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
The electrical resistance of molten lead chloride was measured under controlled Cooling of the me... more The electrical resistance of molten lead chloride was measured under controlled Cooling of the melt to its complete freezing. At the very beginning of the melt solidification unexpected changes in resistance were observed and their dependence on the melt temperature history was studied.
ABSTRACT Absorption, emission and excitation spectra and luminescence decay kinetics of Na(K)GdCe... more ABSTRACT Absorption, emission and excitation spectra and luminescence decay kinetics of Na(K)GdCe, NaGdTb and NaGdMn phosphate glasses and their dependence on the temperature (in the 1.7–300 K range) and on the glass composition have been studied. The processes of energy migration through the Gd3+ ions and following energy transfer in Gd3+-impurity pairs have been compared for the three types of the glasses studied. It has been suggested that the Gd3+ → Tb3+ energy transfer occurs only in the closest pairs through a very short-range exchange interaction, while the Gd3+ → Ce3+ and Gd3+ → Mn2+ energy transfer is possible also in more separated pairs mainly due to the longer-range multipolar Gd3+-impurity interaction.
The crystallization of incongruently melting compounds K,PbCI,, Rb,PbCI,, and Cs,PbCI, from a hig... more The crystallization of incongruently melting compounds K,PbCI,, Rb,PbCI,, and Cs,PbCI, from a high temperature solution, or by a horizontal travelling heater method is investigated and the obtained crystals are characterized by using methods of DTA, X-ray analysis, absorption, and emission spectroscopy.
The present paper deals with preparation, thermal properties and radioluminescence of Ce-doped Na... more The present paper deals with preparation, thermal properties and radioluminescence of Ce-doped Na-Gd phosphate glasses. Thanks to their high radioluminescence intensity, three times greater than that of BGO, these glasses are promising materials for the detection of neutrons, γand X-rays. The glasses with a Gd concentration up to 89 mol% were prepared by a rapid quenching technique in air. Their thermal properties were determined using DSC and temperatures of glass transition were measured in addition using TMA. Temperatures of glass transition, crystallization and melting depend on Gd concentration and they follow the liquidus line in a phase diagram of binary system in which two eutectics and a congruently melting compound exist. High glass-forming ability of this glass system was found evidenced. The glasses containing at least 30 mol% Gd were moisture resistant.
Sensitization role of Gd 3+ ions in energy transfer processes in radio-and photo-luminescence is ... more Sensitization role of Gd 3+ ions in energy transfer processes in radio-and photo-luminescence is described for Tb 3+doped and Gd-enriched Na x Gd y phosphate glasses. Limited (Gd-Gd) n energy migration is obtained and the Gd 3+ -Tb 3+ transfer is explained as due to mainly the (super) exchange interaction. These results are discussed and compared with the situation observed in similar glasses or crystals where transfer processes are mainly due to multi-polar interaction (Gd 3+ -Ce 3+ or Ce 3+ -Gd 3+ ) and more efficient migration among Gd 3+ ions that is observed. r
Influence of the molten state controlled by thermal history of the melt and overheating on melt s... more Influence of the molten state controlled by thermal history of the melt and overheating on melt supercooling was studied experimentally for PbCl 2 , KPb 2 Cl 5 , CsCl and ZnCl 2 . The supercooling of all the molten compounds, except that of CsCl, increased with overheating and reached a maximum degree of supercooling of about 60 K for ZnCl 2 , 60 K for PbCl 2 and 35 K for KPb 2 Cl 5 . Molten CsCl only reached small supercooling, from 2 to 4 K, independent of previous overheating. The influence studies of the thermal history of the melt on ZnCl 2 and KPb 2 Cl 5 supercooling showed that the overheating of the previous experiment influenced levels of supercooling of the following ones. r
We present a model allowing to estimate the so-called time lag of nucleating halide melts using e... 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.
The structure and optical properties of thin films grown by the vacuum co-evaporation of CsI and ... 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
The optical transparency of PbWO 4 single crystals in the short wavelength region between 320 nm ... 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 ...
ABSTRACT Present characteristics of scintillating properties of rare earth aluminum garnets RE3Al... 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.
Optical absorption, photo-and thermo-luminescence measurements were performed on (NaPO3)x(GdPO4)y... more Optical absorption, photo-and thermo-luminescence measurements were performed on (NaPO3)x(GdPO4)y(TbPO4)z (x = 60-77 mol%; y = 20-30 mol%; z = 3-10 mol%) glasses. Pronounced changes of photoluminescence intensity of the leading 542 nm emission line of Tb 3+ were observed during prolonged excitation (irradiation) by 308 nm XeCl excimer laser line into the Gd 3+ 6 P 5=2 excited state. Laser irradiation also gave rise also to optical absorption that peaks at around 5:4 MeV and to a thermoluminescence glow peak at 195 • C. Similar optical absorption and thermoluminescence features were found by ionising (X-ray) irradiation. The results are explained by taking into account energy exchange between the Gd-sub-lattice and deep traps in the glass matrix.
The room temperature spectra of the Faraday rotation and magnetic circular dichroism in a cerium ... more The room temperature spectra of the Faraday rotation and magnetic circular dichroism in a cerium doped yttrium iron garnet (Ce : YIG) are presented. A dramatic change of the magnetoopticai properties due to the substitution of Ce observed in the near infrared and visible regions originates from a strong paramagnetic transition centered near 1.41 eV (0.88 #m).
The single crystalline Lu 3 Al 5 O 12 (LuAG) and Y 3 Al 5 O 12 (YAG) garnet layers doped by Ce 3þ... more The single crystalline Lu 3 Al 5 O 12 (LuAG) and Y 3 Al 5 O 12 (YAG) garnet layers doped by Ce 3þ ions were grown by the liquid phase epitaxy from the flux. The effect of the flux composition, growth conditions, and substrate polishing on the layer morphology, creation of defects, and on optical and emission properties of layers was studied. The defects typical of the epitaxial growth are discussed.
The behavior of an octahedral center created in alkali chloride and bromide single crystals by do... 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.
ABSTRACT Emission and absorption properties of RbPb2Cl5 crystals are reported for the first time ... 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.
Origin of supercoolability in metallic and halide melts is discussed. While the level of supercoo... 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.
We report on spectroscopic investigations of Nd{sup 3+}- and Tb{sup 3+}- doped low phonon energy,... 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
The electrical resistance of molten lead chloride was measured under controlled Cooling of the me... more The electrical resistance of molten lead chloride was measured under controlled Cooling of the melt to its complete freezing. At the very beginning of the melt solidification unexpected changes in resistance were observed and their dependence on the melt temperature history was studied.
ABSTRACT Absorption, emission and excitation spectra and luminescence decay kinetics of Na(K)GdCe... more ABSTRACT Absorption, emission and excitation spectra and luminescence decay kinetics of Na(K)GdCe, NaGdTb and NaGdMn phosphate glasses and their dependence on the temperature (in the 1.7–300 K range) and on the glass composition have been studied. The processes of energy migration through the Gd3+ ions and following energy transfer in Gd3+-impurity pairs have been compared for the three types of the glasses studied. It has been suggested that the Gd3+ → Tb3+ energy transfer occurs only in the closest pairs through a very short-range exchange interaction, while the Gd3+ → Ce3+ and Gd3+ → Mn2+ energy transfer is possible also in more separated pairs mainly due to the longer-range multipolar Gd3+-impurity interaction.
The crystallization of incongruently melting compounds K,PbCI,, Rb,PbCI,, and Cs,PbCI, from a hig... more The crystallization of incongruently melting compounds K,PbCI,, Rb,PbCI,, and Cs,PbCI, from a high temperature solution, or by a horizontal travelling heater method is investigated and the obtained crystals are characterized by using methods of DTA, X-ray analysis, absorption, and emission spectroscopy.
The present paper deals with preparation, thermal properties and radioluminescence of Ce-doped Na... more The present paper deals with preparation, thermal properties and radioluminescence of Ce-doped Na-Gd phosphate glasses. Thanks to their high radioluminescence intensity, three times greater than that of BGO, these glasses are promising materials for the detection of neutrons, γand X-rays. The glasses with a Gd concentration up to 89 mol% were prepared by a rapid quenching technique in air. Their thermal properties were determined using DSC and temperatures of glass transition were measured in addition using TMA. Temperatures of glass transition, crystallization and melting depend on Gd concentration and they follow the liquidus line in a phase diagram of binary system in which two eutectics and a congruently melting compound exist. High glass-forming ability of this glass system was found evidenced. The glasses containing at least 30 mol% Gd were moisture resistant.
Sensitization role of Gd 3+ ions in energy transfer processes in radio-and photo-luminescence is ... more Sensitization role of Gd 3+ ions in energy transfer processes in radio-and photo-luminescence is described for Tb 3+doped and Gd-enriched Na x Gd y phosphate glasses. Limited (Gd-Gd) n energy migration is obtained and the Gd 3+ -Tb 3+ transfer is explained as due to mainly the (super) exchange interaction. These results are discussed and compared with the situation observed in similar glasses or crystals where transfer processes are mainly due to multi-polar interaction (Gd 3+ -Ce 3+ or Ce 3+ -Gd 3+ ) and more efficient migration among Gd 3+ ions that is observed. r
Influence of the molten state controlled by thermal history of the melt and overheating on melt s... more Influence of the molten state controlled by thermal history of the melt and overheating on melt supercooling was studied experimentally for PbCl 2 , KPb 2 Cl 5 , CsCl and ZnCl 2 . The supercooling of all the molten compounds, except that of CsCl, increased with overheating and reached a maximum degree of supercooling of about 60 K for ZnCl 2 , 60 K for PbCl 2 and 35 K for KPb 2 Cl 5 . Molten CsCl only reached small supercooling, from 2 to 4 K, independent of previous overheating. The influence studies of the thermal history of the melt on ZnCl 2 and KPb 2 Cl 5 supercooling showed that the overheating of the previous experiment influenced levels of supercooling of the following ones. r
We present a model allowing to estimate the so-called time lag of nucleating halide melts using e... 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.
The structure and optical properties of thin films grown by the vacuum co-evaporation of CsI and ... 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
The optical transparency of PbWO 4 single crystals in the short wavelength region between 320 nm ... 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 ...
ABSTRACT Present characteristics of scintillating properties of rare earth aluminum garnets RE3Al... 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.
Optical absorption, photo-and thermo-luminescence measurements were performed on (NaPO3)x(GdPO4)y... more Optical absorption, photo-and thermo-luminescence measurements were performed on (NaPO3)x(GdPO4)y(TbPO4)z (x = 60-77 mol%; y = 20-30 mol%; z = 3-10 mol%) glasses. Pronounced changes of photoluminescence intensity of the leading 542 nm emission line of Tb 3+ were observed during prolonged excitation (irradiation) by 308 nm XeCl excimer laser line into the Gd 3+ 6 P 5=2 excited state. Laser irradiation also gave rise also to optical absorption that peaks at around 5:4 MeV and to a thermoluminescence glow peak at 195 • C. Similar optical absorption and thermoluminescence features were found by ionising (X-ray) irradiation. The results are explained by taking into account energy exchange between the Gd-sub-lattice and deep traps in the glass matrix.
The room temperature spectra of the Faraday rotation and magnetic circular dichroism in a cerium ... more The room temperature spectra of the Faraday rotation and magnetic circular dichroism in a cerium doped yttrium iron garnet (Ce : YIG) are presented. A dramatic change of the magnetoopticai properties due to the substitution of Ce observed in the near infrared and visible regions originates from a strong paramagnetic transition centered near 1.41 eV (0.88 #m).
The single crystalline Lu 3 Al 5 O 12 (LuAG) and Y 3 Al 5 O 12 (YAG) garnet layers doped by Ce 3þ... more The single crystalline Lu 3 Al 5 O 12 (LuAG) and Y 3 Al 5 O 12 (YAG) garnet layers doped by Ce 3þ ions were grown by the liquid phase epitaxy from the flux. The effect of the flux composition, growth conditions, and substrate polishing on the layer morphology, creation of defects, and on optical and emission properties of layers was studied. The defects typical of the epitaxial growth are discussed.
The behavior of an octahedral center created in alkali chloride and bromide single crystals by do... 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.
ABSTRACT Emission and absorption properties of RbPb2Cl5 crystals are reported for the first time ... 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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Papers by K. Nitsch