Effect of Bi Doping on the Optical Properties of CdI<Subscript>2</Subscript>

The effect of Bi impurity on the optical absorption and roentgeno-, photo-, and thermoluminescence spectra of CdI₂ crystals grown by the Bridgman-Stockbarger method is studied. CdI₂ activation with BiI₃ produces a number of absorption bands related to electronic transitions of Bi³⁺. Bi produces no emission centers in CdI₂. The 550- to 560-nm luminescence of CdI₂ is due to the radiative recombination of self-trapped anion excitons. The observed changes in spectral distribution and the reduction in light yield upon CdI₂ activation with Bi³⁺ are mainly due to the reabsorption of emission from native centers by activator centers. Under x-ray excitation, CdI₂: Bi³⁺ accumulates a small light sum at shallow trap levels related to native defects.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 7, 2005, pp. 886–891.Original Russian Text Copyright © 2005 by Kravchuk, Novosad, Voitsekhovskaya.     

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.     

Low-temperature luminescent properties of Mn-activated layered cadmium and calcium halides

The luminescent properties of Mn-activated CdCl₂, CdBr₂, CdI₂, and CaI₂ crystals are studied in the range 4.2-200 K. The photo- and roentgenoluminescence spectra of the crystals show red emission bands due to the Mn activator. The excitation spectra and Mn luminescence kinetics are interpreted in terms of the crystal-field theory with consideration for electron paramagnetic resonance data. The red luminescence of the crystals at 4.2 K is attributed to the ⁴ T _1g(⁴ G) ⁶ A _1g(⁶ S) electron-phonon transitions of Mn²⁺. The Racah parameters B and C are determined. The origin of the 600-nm luminescence in CdBr₂:Mn²⁺ under excitation with a nitrogen laser and xenon lamp at 320-360 nm in the range 4.2–90 K is discussed.Translated from Neorganicheskie Materialy, Vol. 41, No. 2, 2005, pp. 230–234.Original Russian Text Copyright © 2005 by Panasyuk, Goncharuk, Kravchuk, S. Novosad, I. Novosad.     

Photoconductivity and luminescence anisotropy in ZnIn<Subscript>2</Subscript>S<Subscript>4</Subscript> and ZnIn<Subscript>2</Subscript>S<Subscript>4</Subscript>:Cu<Superscript>2+</Superscript> single crystals

ZnIn₂S₄ and ZnIn₂S₄:Cu²⁺ single crystals are shown to exhibit considerable photoconductivity and luminescence anisotropy. The mechanism of carrier recombination in the crystals is polarization-dependent. Their spectra can be understood in terms of optical transitions involving donor and acceptor levels. The degree and spectral distribution of the anisotropy can be tuned via doping and alternating growth of the three- and one-layer polytypes.     

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.     

Thermoluminescence characteristics of Sm<Superscript>3+</Superscript> doped NaYF<Subscript>4</Subscript> crystals

Thermoluminescence (TL) characteristics of NaYF₄ crystals doped with Sm³⁺ have been studied after γ-ray irradiation. Dependence of luminescence efficiency on Sm³⁺ concentration and radiation dose has been measured and possible applications of NaYF₄: Sm³⁺ as a novel phosphor for TL dosimetry have been investigated. The efficiency of 0·3 mole% Sm³⁺ doped NaYF₄ crystal has been found to be maximum and comparable with commercial thermoluminescence dosimetric (TLD) materials.     

Recombination luminescence of CaI<Subscript>2</Subscript> crystals activated with Eu<Superscript>2+</Superscript>, Gd<Superscript>2+</Superscript>, Tl<Superscript>+</Superscript>, Pb<Superscript>2+</Superscript>, and Mn<Superscript>2+</Superscript>

The spectral characteristics of thermostimulated luminescence, steady-state roentgenoluminescence and photostimulated luminescence (PSL) buildup and decay kinetics, and the effect of IR irradiation on the roentgenoluminescence yield and glow curves of CaI₂:Eu²⁺, CaI₂:Gd²⁺, CaI₂:Tl⁺, CaI₂:Pb²⁺, CaI₂:Mn²⁺, and CaI₂: Pb²⁺, Mn²⁺ crystals grown by the Bridgman-Stockbarger method have been studied in the temperature range 90–295 K. Coupled with earlier data, the present results on the influence of oxygen and hydrogen impurities on the spectral characteristics of CaI₂ indicate that the activation of calcium iodide with Eu²⁺, Gd²⁺, Tl⁺, Pb²⁺, and Mn²⁺ leads to the formation of cation impurity-native defect complexes, which act as carrier traps and are responsible for the thermostimulated luminescence in the range 150–295 K. IR exposure after 90-K x-ray excitation gives rise to flash PSL and influences the thermostimulated luminescence light sum. The nature of the emission and trapping centers involved and the mechanisms of recombination luminescence excitation in the crystals are discussed.     

Radiation-Induced Effects in Ce<Superscript>3+</Superscript>- and Eu<Superscript>2+</Superscript>-Doped Al<Subscript>5</Subscript>O<Subscript>6</Subscript>N

Polycrystalline Al₅O₆N samples have been prepared by sol–gel synthesis followed by carbothermal reduction and nitridation. X-ray luminescence (XRL) spectra and thermoluminescence (TL) curves of Ce³⁺- and Eu²⁺-doped aluminum oxynitride have been measured in the temperature range 5–380 K and analyzed. Working TL peaks have been detected in the range 150–250 K for the Al₅O₆N:Ce³⁺ sample and in the range 140–200 K for the Al₅O₆N:Eu²⁺ samples. There are also lower temperature peaks: in the ranges 10–60 and 20–100 K. The XRL spectra of the samples have been measured at temperatures of 8 (for the first time) and 300 K.     

Gas-Phase UV Photolysis of CH<Subscript>3</Subscript><Superscript>131</Superscript>I

Gas-phase UV photolysis of ¹³¹I-labeled CH₃I was studied. CH₃ ¹³¹I (228 mg) is completely photolyzed within 5 min under the static conditions at room temperature in an argon atmosphere. The final radioiodine compound formed under these conditions is ¹³¹I₂. The chemical composition of the final products of CH₃I photolysis in air is more complex. Agglomeration corcystallization of the CH₃I photolysis products with NH₄Cl in the gas phase was studied. The results of this study suggest that the main final product of CH₃I photolysis in air is a fine I_xO_y aerosol. In the presence of NH₄Cl, formation of NH₄ ¹³¹I aerosols is possible.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 269–273.Original Russian Text Copyright © 2005 by Kulyukhin, Kulemin, Rumer, Konovalova.     

K<Superscript>+</Superscript> ion conducting properties in the R<Subscript>2</Subscript>O<Subscript>3</Subscript>-KNO<Subscript>3</Subscript> (R: Rare earths) solid solution series

A new type of polycrystalline potassium ion conducting solid electrolyte doped with potassium nitrite as the starting material, was developed. Since cubic rare earth oxides hold reasonably enough interstitial space for bulky K⁺ ion migration in the crystal lattice, an extraordinary high K⁺ ion conductivity was successfully achieved by forming a polycrystalline (1 − x)R₂O₃-xKNO₃ solid solution, which was realized by doping KNO₂ as the KNO₃ state into the interstitial site of cubic rare earth oxide crystal lattice. The potassium ion conductivity of the (1 − x)R₂O₃-xKNO₃ (R: rare earths) solid solution linearly increased with expanding the R₂O₃ crystal lattice and the highest K⁺ ion conductivity was obtained for the 0.653Gd₂O₃-0.347KNO₃ solid solution, which is three orders of magnitude higher than that of a well-known polycrystalline K⁺ ion conducting K₂SO₄ solid and the value exceeds that in the ab conducting plane of a K⁺-β ”-Al₂O₃ single crystal.     

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.     

Visualization of 1.908-μm radiation of a Tm:YLF laser using PbF<Subscript>2</Subscript>-based ceramics doped with Ho<Superscript>3+</Superscript> ions

Visualization of IR radiation of a Tm:YLF laser at 1908 nm in PbF₂ ceramic samples has been investigated. Luminescence spectra of the PbF₂ samples doped with Нo³⁺ exhibited bands at wavelengths of 490, 545, and 650 nm (this red band is the strongest). It is established that at, a low laser intensity, the ⁵I₅ and ⁵I₆ levels are occupied mainly due to the ion–ion energy transfer.     

Thermodynamic study of the Cu-As-S system by EMF measurements with Cu<Subscript>4</Subscript>RbCl<Subscript>3</Subscript>I<Subscript>2</Subscript> as a solid electrolyte

The Cu-As-S system has been studied at temperatures from 300 to 370 K using emf measurements with Cu₄RbCl₃I₂ as a Cu⁺ ion conducting solid electrolyte, and its subsolidus phase diagram has been mapped out, including the ternary compounds Cu₃AsS₄, Cu₆As₄S₉, Cu₄As₂S₅, Cu₃AsS₃, and CuAsS. From the emf data, we have calculated the partial molar thermodynamic functions (D[`(G)]\Delta \bar G, D[`(H)]\Delta \bar H, and D[`(S)]\Delta \bar S) of the copper in the alloys and the standard thermodynamic functions of formation and standard entropies of the ternary compounds.     

X-ray Diffraction Study of the Structure and Defect System of Nominally Pure and Er<Superscript>3+</Superscript>- and Ce<Superscript>3+</Superscript>-Activated (Na<Subscript>0.5</Subscript>La<Subscript>0.5</Subscript>)MoO<Subscript>4</Subscript> Crystals

Nominally pure and activated (Er³⁺ and Er³⁺ + Ce³⁺) sodium lanthanum molybdate single crystals grown by the Czochralski technique from the (Na_0.5La_0.5)MoO₄ melt in different environments and then oxidized in air at 100°C are characterized in detail by x-ray diffraction (lattice parameters and structure refinement by the Rietveld method and single-crystal techniques). The results confirm that (Na_0.5La_0.5)MoO₄ crystallizes in a tetragonal scheelite structure (sp. gr. I₁/a). The crystals (especially unannealed crystals grown in neutral atmosphere) are shown to contain oxygen vacancies. In addition, some of the samples contain Mo vacancies. The Er³⁺ distribution over some of the activated crystals is highly inhomogeneous. As a result, the crystals contain Er-enriched zones with a distorted scheelite structure.     

The nature of optical pumping losses in low-threshold LiF(F<Subscript>2</Subscript>, F<Stack><Subscript>3</Subscript><Superscript>+</Superscript></Stack>) crystal microlasers

The character of optical losses in Li(F₂, F ₃ ⁺ ) crystals were studied for the first time by methods of optical absorption spectroscopy and X-ray diffraction. It is suggested that centers absorbing at 420 nm represent quasi-metallic defects of the F₂F_L type.     

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.     

Effect of coactivation with Dy<Superscript>3+</Superscript> and Yb<Superscript>3+</Superscript> ions on the efficiency of energy storage in Lu<Subscript>2</Subscript>SiO<Subscript>5</Subscript>:Ce<Superscript>3+</Superscript> crystals

Cerium-activated lutetium oxyorthosilicate Lu₂SiO₅:Ce³⁺ (LSO:Ce) and coactivated LSO:Ce,Dy and LSO:Ce,Yb crystals have been synthesized by the sol-gel technique. It is shown that the introduction of coactivator (Yb and Dy) ions influences the energy storage in LSO:Ce, thus making it possible to control the afterglow and thermoluminescence in these crystals. The observed effect is related to the electron properties of coactivator ions (donor against acceptor), which determine the recharge of electron traps in LSO crystals.     

Study of the effect of Li<Superscript>+</Superscript> concentration on the photoluminescence properties of Y<Subscript>2</Subscript>O<Subscript>3</Subscript>:Eu<Superscript>3+</Superscript> phosphors

Y₂O₃:Eu³⁺ phosphors were prepared by hydrothermal method. Effect of the doping concentration of Eu³⁺ on the photoluminescence properties of Y₂O₃:Eu³⁺ phosphor was studied in details. It was found that the strongest emission intensity is achieved as atomic ratio of Y³⁺ to Eu³⁺ is 8. As concentration of Eu³⁺ exceeds the critical concentration, the emission intensity decreases dramatically due to the concentration quenching of Eu³⁺. Also, the effect of Li⁺ on the photoluminescence performance of the Y₂O₃:Eu³⁺ phosphor is studied in this work. According to the results, the doping of Li⁺ may greatly improve the PL performance of the Y₂O₃:Eu³⁺ phosphors due to the flux effect and improved crystallinity caused by the doping of Li⁺.     

Emission analysis of Pr<Superscript>3+</Superscript> &; Ho<Superscript>3+</Superscript>: Ca<Subscript>4</Subscript>GdO(BO<Subscript>3</Subscript>)<Subscript>3</Subscript> powder phosphors

Emission spectral results of Pr³⁺ & Ho³⁺ ions doped Ca₄GdO(BO₃)₃ powder phosphors are reported here. XRD, SEM and FTIR measurements have been carried out for them. The emission spectrum of Pr³⁺: Ca₄GdO(BO₃)₃ has shown an emission transition ¹D₂ → ³H₄ at 606 nm with λ_exci = 480 nm (³H₄ → ³P₀) and Ho³⁺: Ca₄GdO(BO₃)₃ phosphor has shown an emission transition ⁵S₂ → ⁵I₈ at 549 nm with λ_exci = 447 nm (⁵I₈ → ⁵F₁). Emission performances of these two phosphors have been explained in terms of energy level diagrams.     

Temperature effect on the photoluminescence intensity and Eu<Superscript>2+</Superscript> excited state lifetime in EuGa<Subscript>2</Subscript>S<Subscript>4</Subscript> and EuGa<Subscript>2</Subscript>S<Subscript>4</Subscript>:Er<Superscript>3+</Superscript>

The photoluminescence (PL) spectra and Eu²⁺ excited state lifetime of EuGa₂S₄ and EuGa₂S₄:Er³⁺ have been studied in the range 78–500 K. The spectra show a band at 545 nm, due to the 4f ⁶5d → 4f ⁷(⁸ S _7/2) transition. With increasing temperature, the full width at half maximum Γ(T) of the PL band of EuGa₂S₄ and EuGa₂S₄:Er³⁺ crystals increases from 0.15 to 0.22 and from 0.13 to 0.19 eV, respectively. Over the entire temperature range studied, Γ(T) is a linear function of T ^1/2. The 545-nm emission intensity and Eu²⁺ excited state lifetime in EuGa₂S₄ and EuGa₂S₄:Er³⁺ vary exponentially with temperature. The luminescence quenching energies evaluated from the Arrhenius plots of I(10³/T) and τ(10³/T) coincide (0.10 eV) within the error of determination.