Extraction of U(VI) and Th(IV) ions from nitric acid solutions with <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′,<Emphasis Type="Italic">N</Emphasis>′-tetra-2-ethylhexylglutaramide

N,N,N′,N′-Tetra-2-ethylhexylglutaramide (TEHGA) was used as a new extractant for the extraction of U(VI) and Th(IV) from nitric acid solutions. Toluene was found to be the most suitable diluent for TEHGA. The extraction of nitric acid was also studied. The influence exerted on the distribution ratio (D) of U(VI) and Th(IV) by the concentrations of HNO₃, TEHGA, and LiNO₃ as salting-out agent, and also by the equilibration time, temperature, and kind of diluent was examined. Good U–Th separation can be achieved using 2–3 M HNO₃. The results obtained show that U(VI) and Th(IV) are mainly extracted as UO₂(NO₃)₂·2TEHGA and Th(NO₃)₄·TEHGA, respectively. The IR spectra of the extracted species were analyzed. The thermodynamic functions of the process were calculated. Back-extraction of U(VI) and Th(IV) from the organic phases was also studied.     

Synthesis,Structure, and Superconductivity of (La1.5Pb0.5−<Emphasis Type="Italic">x</Emphasis>Sr<Emphasis Type="Italic">x</Emphasis>)CuO<Emphasis Type="Italic">z</Emphasis>

The substitution of strontium for lead in the material (La_1.5Pb_0.5?xSr _x )CuO _z , x = 0–0.15 has been carried out. A stable and reproducible single phased superconducting materials can be obtained inside an evacuated quartz tube. The X-ray diffraction pattern shows that the superconducting phase can be indexed on the basis of an orthorhombic symmetry (F_mmm) for x = 0 and on the basis of tetragonal symmetry (I_4/mmm) for x > 0. The transition temperature T _c increases as the strontium substitution parameter x increases. We observed the maximal T _c around x = 0.15 with 38 K with fairly large Meissner volume fraction of 38% (FC).     

<Emphasis Type="Italic">T</Emphasis>–<Emphasis Type="Italic">P</Emphasis> Phase Diagram of Nitrogen at High Pressures

By employing a mean field model, calculation of the T–P phase diagram of molecular nitrogen is performed at high pressures up to 200 GPa. Experimental data from the literature are used to fit a quadratic function in T and P, describing the phase line equations which have been derived using the mean field model studied here for N₂, and the fitted parameters are determined. Our model study gives that the observed T–P phase diagram can be described satisfactorily for the first-order transitions between the phases at low as well as high pressures in nitrogen. Some thermodynamic quantities can also be predicted as functions of temperature and pressure from the mean field model studied here and they can be compared with the experimental data.     

Subnanosecond impact-ionization switching of silicon structures without <Emphasis Type="Italic">p</Emphasis>–<Emphasis Type="Italic">n</Emphasis> junctions

It is shown that an application of a fast-rising high-voltage pulse to an n ⁺–n–n ⁺ silicon structure leads to subnanosecond avalanche breakdown, generation of electron–hole plasma throughout the entire structure, and structure switching to the conducting state in a time of about 100 ps. The predicted effect is similar to the delayed avalanche breakdown of reverse-biased p ⁺–n–n ⁺ diode structures; however, it is implemented in a structure without p–n junctions.     

Structural Parameters and Spin Filtering Properties of Ga<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>(<Emphasis Type="Bold">M</Emphasis>)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>P compound

In this work, we have explored the structural and magnetic properties of GaP-based diluted magnetic semiconductors (DMSs). Based on first-principle density functional theory (DFT) calculations and using a full potential linearized augmented plane wave (FP-LAPW) method in generalized gradient approximation (GGA), some significant structural and magnetic properties of Ga _1?x (M) _x P compound as DMS are investigated. In this compound, M is a transition element such as vanadium (V), manganese (Mn), cobalt (Co), and copper (Cu) with a concentration of X. We have calculated the structural parameters such as the equilibrium lattice constant and bulk modulus of the compound. Furthermore, the spin polarization and magnetic moments are studied. We have found that by increasing the atomic number of the transition element, the lattice constant reduces, except for that of Cu, and compressibility improved in comparison with GaP. Moreover, with X=25 %, the Ga_0.75(M)_0.25P compound becomes more stable by increasing the atomic number of the transition element M. The study of the electronic properties of the compound indicates that the main contribution in total density of states near Fermi level is related to the 3d orbitals of the transition elements and the highest magnetic moment is for Mn-doped GaP.     

Thermal conductivity of Er<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Sn<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Se (<Emphasis Type="Italic">x</Emphasis> ≤ 0.025) solid solutions

The thermal conductivity of Er _x Sn_{1 ? x} Se solid solutions has been measured at temperatures from 80 to 360 K. The results have been used to evaluate the electronic and lattice components of thermal conductivity for elastic carrier scattering, parabolic bands, and arbitrary degeneracy. With increasing erbium content and temperature, both the electronic and lattice components decrease considerably. Long-term annealing increases both components. It follows from the present experimental data that heat conduction in Er _x Sn_{1 ? x} Se is mainly due to phonons and that the observed rise in thermal resistance with Er content is due to phonon-phonon and paramagnetic-ion scattering.     

Homogeneity of high-resistivity <Emphasis Type="Italic">p</Emphasis>-Si<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>〈Au〉 crystals

p-Si_{1 ? x} Ge _x crystals have been diffusion-doped with gold. Gold diffusion in the p-Si_{1 ? x} Ge _x 〈Au〉 samples and their electrical properties have been studied. The results demonstrate that the highest gold concentration in the crystals can be achieved in the temperature range 1000–1050°C. An expression has been derived which indicates that, all other factors being the same, compensation with Au, an amphoteric impurity, insures better homogeneity compared to codoping with acceptor and donor impurities. The hole concentration homogeneity in gold-compensated samples is at the same level as or even better than that in the uncompensated material.     

Boundary Conditions for Thermoelectric Cooling in <Emphasis Type="Italic">p</Emphasis>–<Emphasis Type="Italic">n</Emphasis> Junction

The article is devoted to analysis of the boundary conditions for the Peltier effect in semiconductors containing potential barriers (p–n junction). The full system of boundary conditions, taking into consideration the presence of nonequilibrium charge carriers, is offered. The surface recombination of charge carriers is taken into account for both the electric current and the propagation of heat.     

Raman spectroscopy determination of carrier concentration in <Emphasis Type="Italic">n</Emphasis>-In<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ga<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>As epitaxial films

We have studied in detail the coupled phonon-plasmon mode Raman spectra of n-In _x Ga_{1 − x} As with n in the range 10¹⁷ to 10¹⁹ cm⁻³. The results indicate that the behavior of the high-frequency mode L ₊ can be described in terms of coupled modes in the Drude approximation. The proposed theory and experimental data are used to estimate the carrier concentration in the solid solution and its composition.     

Preparation and Properties of Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Hg<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Te

Mn _x Hg_{1 ? x}Te (x = 0.05, 0.12) single crystals were grown by solid-state recrystallization, and their axial and radial homogeneity was assessed by optical, electrical, and electron-microscopic measurements. The crystals are p-type, with a hole concentration of (4.3–5.3) × 10²² m^?3 and Hall mobility in the range (410–570) × 10^?4 m²/(V s).     

Growth and properties of single crystals of Si<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> (0 < <Emphasis Type="Italic">x</Emphasis> < 0.35) solid solutions

Single-crystalline Si_{1 − x} Ge _x ingots with a germanium content of up to 35 at. %, a diameter of 10mm, and a length of up to 10 cm were grown using the crucibleless float-zone melting technique. The ingots had a homogeneous distribution of germanium and a low density of dislocations. The material was characterized with respect to the structure and electrical properties. The resistivity and the carrier lifetime, mobility, and concentration in Si_{1 − x} Ge _x single crystals have been studied as functions of the germanium content.     

Synthesis and structural properties of AgCl<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Br<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> (<Emphasis Type="Italic">x</Emphasis> = 0.5–0.8) solid solutions

The properties of AgCl_{1 - x} Br_x ( x = 0.5-0.8) solid solutions prepared by the Bridgman-Stockbarger method are studied using a variety of techniques (x-ray diffraction, microstructural examination, chemical analysis, and x-ray microanalysis). The lattice parameter of the solid solutions is found to exhibit a negative deviation from additivity. The effects of composition and preparation conditions on the structural properties of the solid solutions are discussed. The structural characteristics of abrasively polished surfaces of the samples are shown to be influenced by the preparation conditions.Translated from Neorganicheskie Materialy, Vol. 41, No. 1, 2005, pp. 78–87. Original Russian Text Copyright © 2005 by Artjushenko, Baskov, Golovanov, Kuzmicheva, Lisitskii, Musina, Polyakova, Sakharov, Sakharova.     

Structural and magnetic properties of Cr<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>V<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Te (<Emphasis Type="Italic">x</Emphasis> = 0−0.4) solid solutions

Cr_1?x V _x Te solid solutions with a hexagonal structure (NiAs type) have been obtained in the composition range x = 0?0.4 by direct melting of elemental mixtures, followed by annealing and quenching. The 80-K magnetic moment is found to decrease from 2.4μ_B in CrTe to 1.52μ_B in Cr_0.6V_0.4Te. The Curie temperature varies from 342 K to 321 K, respectively.     

Optical and transport properties of Fe-doped Cd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Hg<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Se (<Emphasis Type="Italic">x</Emphasis> = 0.35)

The optical and transport properties of Fe²⁺-doped Cd _x Hg_1?x Se crystals with a midgap Fe²⁺ level have been studied. The results demonstrate that Fe²⁺ ions influence both the optical and transport properties of Cd _x Hg_1?x Se〈Fe²⁺〉. The observed optical absorption bands are due to a donor Fe²⁺ level in the band gap, with a depth E _Fe = 0.21 eV, and to band-band transitions. Thermal anneals in Hg and Se vapors have different effects on the carrier concentration and mobility in the crystals. The effect of annealing on the transport properties of the Fe²⁺-doped crystals differs from that for undoped crystals and is governed by the state of point defects.     

Investigating the nanomechanical properties and reversible color change properties of the beetle <Emphasis Type="Italic">Dynastes</Emphasis> <Emphasis Type="Italic">tityus</Emphasis>

The wing cases (elytra) of Dynastes tityus are able to change coloration from yellow-green in a dry state to deep brown in a wet state due to different degrees of water absorption. An environmental scanning electron microscope was used to investigate the elytra’s reversible color change properties. Because the elytra cuticle has a spongy structure that is composed of laminated chitin and protein, a UV–Vis–NIR spectrophotometer was used to investigate the elytra’s optical properties. The width of the curve peak gradually decreased from 60 to 10 nm when the color of the elytra varied from deep brown to yellow-green. In a humid environment, air between the voids was replaced by water with a higher refractive index that induced an elytra color changed from yellow-green to deep brown. Interestingly, when both humidity and elytra color changed, the elytra’s mechanical properties varied too. When the humidity of the environment changed from 100 to 34%, the reduced modulus (E _r) and hardness (H) of the elytra increased 230 and 440%, respectively. The storage modulus (E′) of the elytra is 1.98 ± 0.65 and 1.17 ± 0.22 GPa in yellow-green and deep brown color at 10 Hz, respectively, while their loss modulus (E″) is similar. tan δ of deep brown elytra is 0.072 ± 0.017, which is nearly two times higher than that of yellow-green. It can be demonstrated that when the elytra’s color turns to yellow-green, they are more elastic with less energy loss. The relationship between the elytra’s mechanical properties and structure color will not only help us gain insight into the biological functionality of the color change but also inspire the designs of artificial biomimetic devices.     

Enhanced Superconductivity in Double-Doping Cu<Subscript>0.15</Subscript>TaSe<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript><Emphasis Type="Italic">S</Emphasis><Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>

Superconducting Cu _x TaSe₂(x=0.05, 0.15) and Cu_0.15TaSe_2?x S _x (x=0, 0.5, 1, 1.5) single crystals have been systematically fabricated by a chemical vapor transport method. It is found that the double doping in TaSe₂, i.e., the simultaneous intercalation of Cu and substitution of Se by S, can substantially enhance the superconducting transition temperature. Transport property measurements give evidence of the coexistence and competition of charge density wave state and superconductivity in Cu _x TaSe₂ which provide meaningful information to understand the complex electronic states in this system. The parallel shift and the fan-shape broadening behaviors are observed in the superconducting transition curves under magnetic fields of Cu_0.15TaSeS and TaSeS, respectively, indicating an increase of coherence length and suppression of superconducting fluctuation induced by copper intercalation.     

Superconductivity in a Correlated <Emphasis Type="Italic">E</Emphasis>⊗<Emphasis Type="Italic">e</Emphasis> Jahn–Teller System

By numerically solving the Eliashberg equation in the RPA as well as employing the Landau’s theory for phase transitions, we have investigated superconductivity, especially its pairing character, in a two-orbital Hubbard model coupled with E?e Jahn–Teller phonons on a two-dimensional square lattice at half filling. If the electron hopping between neighboring sites keeps the orbital character invariant in this E?e Jahn–Teller crystal, we find that a new superconducting phase characterized by the pairing of spin singlet, orbital singlet, and odd in momentum space, named a chiral p-wave pairing, is brought about by the collaboration of orbital fluctuations enhanced mainly by the electron–phonon interaction with spin fluctuations induced by the electron–electron one.     

Structure and photoelectric properties of Si<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Sn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> epilayers

Epitaxial layers of n-type Si_{1 − x} Snx (0 ≤ x ≤ 0.04) solid solution were grown by liquid phase epitaxy from tin-based solution melt confined between two horizontal Si(111) single crystal silicon substrates. The structure of epilayers was determined and the photosensitivity spectra of pSi-nSi_{1 − x} Snx (0 ≤ x ≤ 0.04) structures were studied at various temperatures. It is established that Si_0.96Sn_0.04 films have a perfect single crystal structure with (111) orientation and a subgrain size of 60 nm. The photosensitivity edge of the pSi-nSi_0.96Sn_0.04 structure is shifted to longer wavelengths as compared to that of the pSi-nSi structure. The photosensitivity of the pSi-nSi_0.96Sn_0.04 structure in the impurity absorption range depends on the temperature.     

Thermal expansion and isothermal compressibility of TlGaSe<Subscript>2(1 −<Emphasis Type="Italic">x</Emphasis>)</Subscript>S<Subscript>2<Emphasis Type="Italic">x</Emphasis></Subscript> (<Emphasis Type="Italic">x</Emphasis> = 0.1, 0.2)

The temperature dependences of the thermal expansion coefficient and isothermal compressibility for TlGaSe_{2(1 ? x)}S_2x (x = 0.1, 0.2) solid solutions show an anomaly attributable to a second-order phase transition. The thermal expansion data have been used to evaluate the Debye characteristic temperature Θ, rms atomic displacement, and specific heat difference of the solid solutions.     

Synthesis and properties of SrFe<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>M<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>3 − <Emphasis Type="Italic">z</Emphasis></Subscript> (M = Mo,W) perovskites

We have synthesized SrFe_{1 ? x} M _x O_{3 ? z} (M = Mo, W; 0 < x ≤ 0.5) solid solutions. Our results indicate that the introduction of stable MO₆ octahedra narrows the range of oxygen stoichiometries of the material and suppresses the perovskite-brownmillerite structural phase transition at low temperatures and oxygen partial pressures. We have studied the thermal stability of the synthesized materials in a reducing atmosphere and the effect of oxygen stoichiometry on their electronic and oxygen-ionic conductivity and phase transformations.