Binding energies of Eu2+ and Eu3+ ions in β-Ca2SiO4 doped with europium

β-Ca₂SiO₄ doped with Eu²⁺and Eu³⁺was synthesized by solid state reaction. Europium replaces Ca²⁺ ions either as Eu²⁺ or Eu³⁺, both occupying two not equivalent sites; seven fold and eight fold coordinated by O²⁻. β-Ca₂SiO₄:Eu²⁺, β-Ca₂SiO₄:Eu³⁺ and β-Ca₂SiO₄:Eu²⁺, Eu³⁺ samples were investigated by structural and spectroscopic methods. Specifically it has been shown that luminescence spectra of the β-Ca₂SiO₄:Eu²⁺, Eu³⁺ system were a superposition of the Eu²⁺ and Eu³⁺ emission and were independent of temperature from 18 K to ambient. To explain this effect the short distance compensation of the Eu³⁺ replacing Ca²⁺ in the β-Ca₂SiO₄ is discussed. It is argued that such compensation has to causes the conduction and valence bands bend. The existence of stable Eu²⁺ and Eu³⁺ replacing Ca²⁺ ion in lattice is discussed by consideration of the energies of the ground states of the Eu²⁺ and Eu³⁺, the Fermi energy and the energy necessary for creation of compensation defect.     

Anisotropy in the electrical properties of zirconium doped α -Fe2O3 single crystals

The electrical properties of zirconium doped α -Fe₂O₃ single crystals have been investigated from 470 up to 1300 K.As for the pure crystal, an anisotropy appears for the conductivity between the [001] direction and the (001) plane, although lowered by the dopant.Combining the results of electrical conductivity, thermoelectric power and complex impedance measurements, it was established that there was no significant kinetic contribution of the electrons and that their mobility was lower than a few tenths of cm²V⁻¹s⁻¹.     

Effect of γ-radiation on optical properties of Eu2+ ions in the KCl: Eu2+ system

Emission spectra and luminescence time decay of Eu²⁺ ions in KCl crystals annealed at 873 K and quenched to room temperature before irradiation were measured at 80 K after -irradiation which was performed at 295 and 200 K. The results are consistent with radiation-induced aggregation of the original isolated europium dipoles.     

Extrinsic luminescence centers in CdI2 crystals doped with PbI2 (10−4 to 1 mol %)

We have studied the luminescence properties of PbI₂ doped (10^?4 to 1 mol %) CdI₂ crystals in the temperature range 4.2–90 K and those of 2H- and 4H-PbI₂ crystals at 90 K. The results demonstrate that the Pb atoms produce impurity centers in the form of isolated Pb²⁺ ions and 4H-PbI₂ nanocrystals located in the plane of the layers or along linear structural defects of CdI₂. The formation of PbI₂ nanocrystals was confirmed by atomic force microscopy. We discuss excitonic and electron-hole mechanisms of energy transfer to luminescence centers.     

Reversible control of the electronic density of states at the Fermi level of Ca3Co4O9+δ misfit-layered oxide single crystals through O+/H+ plasma exposure

Misfit-layered Ca₃Co₄O₉ crystals were grown and characterized via XRD, SEM, and photo-emission spectroscopy (PES). The evolution of the intensity at the Fermi level (E _F) with varying oxygen content was studied by PES. Oxygen species were successfully introduced and removed through O⁺ and H⁺ microwave-plasma (2.45 GHz, 2–5 mbar) treatments, respectively. A 5 min O⁺ plasma exposure was observed to result into a drastic enhancement in the E _F intensity, demonstrating the influence of oxygen content to the charge carrier population in layered cobalt-oxide materials.     

Growth and magnetic characterization of large R2NiO4+δ (R=Pr, Nd) single crystals

To study the static and dynamic properties of the charge stripe phases in the nickelates by neutron scattering, single crystals are needed with a large volume (>1 cm³). We will report the optimization and growth of large R₂NiO₄₊ (R=Pr, Nd) crystals by the floating-zone technique in an image furnace. Crack-free single crystals of diameter 8–10 mm and length 80–90 mm have been obtained. The phase-purity of the crystals has been checked by powder X-ray diffraction, and information on the crystal quality has been obtained by X-ray and neutron diffraction. We will give an account of our investigations into the conditions needed to obtain the highest quality crystals, and we will discuss the magnetic studies by SQUID magnetometry.     

Synthesis and stability of α-tricalcium phosphate doped with dicalcium silicate in the system Ca3(PO4)2–Ca2SiO4

The aim of this study was to synthesize materials of α-tricalcium phosphate doped with small amounts of dicalcium silicate, by solid state reaction, at high temperature and slow cooling to room temperature. The obtained materials were characterized by X-ray diffraction, Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy, showing that there is a region between 0.5 and 4.0 wt.% of dicalcium silicate where solid solution α-tricalcium phosphate (α-TCPss) is stable to room temperature.     

Effect of Nonstoichiometric Disorder on the Upper Critical Field in Electron Doped Nd2−x Ce x CuO4+δ Single Crystals

Temperature dependences of the electrical resistivity measured in different magnetic fields (B ∥ c, J ∥ ab) of electron doped Nd_2−x Ce _x CuO_4+δ single crystals with different cerium concentration (x=0.15, 0.17, and 0.20) and oxygen content (δ) were studied in a temperature range of 1.8–40 K. It was found that the slope of the upper critical field decreases with the increase of the disorder in the system. So, we can distinguish experimentally d-wave and anisotropic s-wave superconductors. Moreover, the slope of the upper critical field and critical temperature decrease with increase of the disorder parameter like in d-wave superconductors with anisotropic scattering.     

Influence of Soaking in the Molten (Li0.62K0.38)2CO3Eutectic on the Structure and Conductivity of LiMnxFe1 – xO2and Li1 – yMnyFeO2 + δ

The phase composition, structure, and 920-K electrical conductivity of LiMn _x Fe_{1 – x} O₂(0 < x 1) and Li_{1 – y} Mn _y FeO_{2 +} (0 < y 1) materials prepared by solid-state reactions in air at 1270 K were studied before and after soaking in molten (Li_0.62K_0.38)₂CO₃. The highest conductivity of 32 S/m was found in the spinel solid solution Li_0.2Mn_0.8FeO_{2 +} ( = 2/3). Soaking in the carbonate melt converted all Li_{1 – y} Mn _y FeO_{2 +} samples into rocksalt solid solutions and reduced their conductivity.     

Improvement of the Intergranular Pinning Energy in the (BiPb)2Sr2Ca2Cu3O10+δ Superconductors Doped with High Valancy Cations

In the present work, Bi?CPb?CV?CSr?CCa?CCu?CTi?CO bulk samples with nominal composition (BiPb)₂V _x Sr₂Ca₃Cu_4?y Ti _y O_12+?? with x=0.1 and y=0.050, 0.10, 0.2, and 0.3 have been prepared by the melt-quenching method. The magnetoresistance of the samples has been measured for different values of the applied magnetic field. The thermally activated flux creep model has been studied in order to calculate the flux pinning energies. The flux pinning energies calculated increase with increasing Ti-content, and decrease with applied magnetic field.     

Dynamics of optical solitons,multipliers and conservation laws to the nonlinear schrödinger equation in (2+1)-dimensions with non-Kerr law nonlinearity

This work studies the (2 + 1)-dimensional nonlinear Schrödinger equation which arises in optical fibre. Grey and black optical solitons of the model are reported using a suitable complex envelope ansatz solution. The integration lead to some certain conditions which must be satisfied for the solitons to exist. On applying the Chupin Liu's theorem to the grey and black optical solitons, we construct new sets of combined optical soliton solutions of the model. Moreover, classification of conservation laws (Cls) of the model is implemented using the multipliers approach. This is achieved by constructing a set of first-order multipliers of a system of nonlinear partial differential equations acquired by transforming the model into real and imaginary components are derived, which are subsequently used to construct the Cls.     

Study on the interaction between a dislocation and impurities in KCl:Sr<Superscript>2+</Superscript> single crystals by the Blaha effect—Part IV influence of heat treatment on dislocation density

Strain-rate cycling tests associated with ultrasonic oscillation were carried out at 80–239 K for two kinds of KCl:Sr²⁺ (0.05 mol.% in the melt) single crystals: one is a quenched specimen and the other an annealed one. In this study, it was found that the density of moving dislocation is not influenced by the heat treatment. Furthermore, the increase in forest dislocation density for the annealed specimen seemed to be remarkable under the compression test, compared with that for the quenched specimen. As a result, the strain-hardening rate increased and the extent of plastic deformation region became short at a given temperature by annealing the quenched specimens. The investigation concerning forest dislocation density was conducted on the basis of the which will represent the variation of the strain-rate sensitivity due to dislocation cuttings with shear strain.     

X-ray absorption spectroscopy studies of the Ni ion of Li(Ni0.8Co0.15Al0.05)0.8(Ni0.5Mn0.5)0.2O2 with a core–shell structure and LiNi0.8Co0.15Al0.05O2 as cathode materials

Core–shell materials have attracted a great deal of interest since core–shell particles have superior physical and chemical properties compared to their single-component counterparts. The cathode material Li(Ni_0.8Co_0.15Al_0.05)_0.8(Ni_0.5Mn_0.5)_0.2O₂ (LNCANMO) with a core–shell structure was synthesized via a co-precipitation method and investigated as the cathode material for lithium ion batteries. The core–shell particle consisted of LiNi_0.8Co_0.15Al_0.05O₂ (LNCAO) as the core and LiNi_0.5Mn_0.5O₂ as the shell. The cycling behavior between 2.8 and 4.3 V at a current of 0.1 C-rate showed a reversible capacity of ～195 mAh g^?1 with little capacity loss after 50 cycles. Extensive assessment of the electronic structures of the LNCAO and LNCANMO cathode materials was carried out using X-ray absorption spectroscopy (XAS). XAS has been used for structure refinement on the transition metal ion of the cathode. In particular, XAS studies of electrochemical reactions have been done from the viewpoint of the transition metal ion. In this study, Ni K-edge XAS spectra of the charge and discharge processes of LNCAO and LNCANMO were investigated.     

Investigation of magnetic properties of Fe61Co8Zr4−xY2+xNi5Nb5B15 amorphous alloys (x = 0, 1) in the form of ribbons

Amorphous Fe₆₁Co₁₀Zr_4?xY_2+xNb₅B₁₅ (x = 0, 1) samples in the form of a ribbon with a thickness of approximately 30 μm and a width of about 4 mm have been investigated. The ribbons were obtained by a single roller melt-spinning method with the wheel linear velocity equal to 35 m/s. Microstructural studies, using X-ray spectroscopy, confirmed that samples in the as-quenched state were fully amorphous. Measurements carried out using a vibrating sample magnetometer allowed values of coercivity and saturation magnetization to be obtained. On the basis of performed measurements, it can be stated that Fe₆₁Co₈Zr₄Y₂Ni₅Nb₅B₁₅ alloy exhibits superior soft magnetic properties compared with the Fe₆₁Co₈Zr₃Y₃Ni₅Nb₅B₁₅ alloy. The former alloy possesses: a higher value of saturation magnetization, almost double the value of magnetic permeability, approximately half the value of coercivity and substantially smaller core losses than the latter alloy.     

Influence of conditions on the potential of the couple of nonoxygenated U5+/U4+ ions bound in complexes with the P2W17O 6110? and SiW11O 398? anions

The formal potential of the couple of nonoxygenated U⁵⁺/U⁴⁺ ions bound in complexes with unsaturated heteropoly anions (HPAs) P₂W₁₇O₆₁¹⁰⁻ (I) and SiW_{11 O39}⁸⁻ (II) in 0–1 M NaNO₃ and 1 M (NaCl + HCl) in the range of pH 0.7–4.7 was measured. In 1 M NaNO₃ solutions at pH 4.7–3.0 for I and 4.3–3.9 for II, the formal potentials are constant: 0.820 and 0.730 V, respectively. They preserve approximately the same value with a decrease in pH to 0.7 in 1 M (NaCl + HCl). The potential noticeably decreases with a decrease in the NaNO₃ or NaCl concentration from 1 M to 0 (pH 4.1–4.7): to 0.09 and 0.05–0.06 V for I and II, respectively. Approximate constancy of the potential of the U⁵⁺/U⁴⁺ couple with a decrease in pH to 1 and lower distinguishes this couple from the M⁴⁺/M³⁺ couples (M = Ce, Am, Bk) whose potential appreciably grows with increasing acidity. This is due to the fact that the U⁵⁺ and M⁴⁺ ions in acid solutions remain in the form of complexes with the ratio M: HPA = 1: 2, whereas the M³⁺ ions pass into the form of 1: 1 complexes. Thus, variation of the formal potentials of all the M ^{n + 1}/M ⁿ⁺ couples in the presence of H⁺ and Na⁺ ions is associated with variation of the stability constants of the complexes M(HPA)₂, which, in turn, is caused by interaction of single-charged ions with HPA. However, the H⁺ and Na⁺ ions interact with HPA by different mechanisms and therefore affect the potential of the U⁵⁺/U⁴⁺ couple differently. Original Russian Text ? V.P. Shilov, A.B. Yusov, A.M. Fedoseev, Ph. Moisy, 2008, published in Radiokhimiya, 2008, Vol. 50, No. 5, pp. 393–396.     

On the Presence of Cu1+ in the Superconducting (Hg,M)Sr2CuO4+δ; M = Cr, Mo, or Re

The Cu K-edge measurements on the optimum T _c 1201 compounds (Hg_1–x M _x )Sr₂CuO₄₊ (M = Cr, Mo, or Re; 0.10 x 0.30) show besides Cu²⁺ (predominant) a very weak but distinct signature of Cu¹⁺, only in the superconducting (SC) samples. The Cu¹⁺ feature is conspicuously absent when these compositions are non-superconducting because of different processing conditions. Our finding of monovalent Cu in SC (Hg,M)/Sr-1201 favors the presence of Cu at the Hg-site and this seems to facilitate superconductivity in these cuprates.     

Growth of bulk β-BaB<Subscript>2</Subscript>O<Subscript>4</Subscript> crystals of high optical quality in the BaB<Subscript>2</Subscript>O<Subscript>4</Subscript>-NaBaBO<Subscript>3</Subscript> system

Phase equilibria along the BaB₂O₄-NaBaBO₃ join of the BaO-B 2 O 3 -Na 2 O system are studied by differential thermal analysis and modified visual thermal analysis. The join is shown to be suitable for growing - BaB₂O₄ crystal of high optical quality.Translated from Neorganicheskie Materialy, Vol. 41, No. 1, 2005, pp. 64–69. Original Russian Text Copyright © 2005 by Kokh, Kononova, Fedorov, Bekker, Kuznetsov.     

Excitation of the uranyl ion in oxidation of U(IV) with xenon difluoride in frozen aqueous solutions of sulfuric acid: IV. Effect of F<Superscript>−</Superscript> and UO<Stack><Subscript>2</Subscript><Superscript>2+</Superscript></Stack> ions

A specific feature of U(IV) oxidation with xenon difluoride in aqueous H₂SO₄ solutions is low-temperature chemiluminescence (CL), which in the course of warming the sample quickly cooled to 77 K is recorded starting from 165 K and reaches a maximum at about 200 K. Exothermic phase transitions, crystallization of the ice + H₂SO₄·4H₂O and ice + H₂SO₄·6.5H₂O eutectics, occur in the same temperature range. The data (temperature dependences of the chemiluminescence intensity and simultaneously recorded DTA curves) obtained in experiments with variation of the rate of mixing and cooling the solutions and of the concentrations of H₂SO₄ and F^? and UO ₂ ²⁺ ions are well explicable by the catalytic activity of the juvenile surface of H₂SO₄ crystal hydrates toward low-temperature reaction of U(IV) with XeF₂.