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.     

Phase transformation of <Emphasis Type="Italic">p</Emphasis>-Cd<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>GeAs<Subscript>2</Subscript> single crystals at 5.5 GPa

The electrical resistivity and Hall coefficient of oriented single-crystal p-Cd_{1 − x} Mn _x GeAs₂ samples have been measured at high pressures. The results indicate that the crystals undergo a reversible structural transformation at 5.5 GPa, which is independent on the sample orientation.     

Study of gel grown mixed crystals of Ba<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ca<Subscript>(1−<Emphasis Type="Italic">x</Emphasis>)</Subscript>(IO<Subscript>3</Subscript>)<Subscript>4</Subscript>

The growth of mixed crystals of Ba _x Ca_1−x (IO₃)₄ were carried out with simple gel method. The effect of various parameters such as pH of gel solution, gel concentration, gel setting time, concentration of reactants on the growth was studied. Crystals having different morphologies and habits were obtained. The grown crystals were characterized by XRD, FT-IR, EDAX, TGA, DTA and DSC.     

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.     

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.     

Thermoelectric properties of TlIn<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Eu<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Te<Subscript>2</Subscript> crystals

The thermoelectric properties of TlIn_{1 ? x} Eu _x Te₂ (0 < x ≤ 0.09) solid solutions have been studied at temperatures from 300 to 500 K. The results indicate that the thermoelectric figure of merit of the alloys increases with temperature and europium content.     

Photoelectric properties of TlIn<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Pr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Se<Subscript>2</Subscript> (0 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 0.04) single crystals

TlIn_{1 ? x} Pr _x Se₂ (0 ≤ x ≤ 0.04) single crystals have been grown, and their photoelectric properties have been studied. The results have been used to determine the band gap and photosensitivity range of the crystals.     

Thermodynamic properties of (TeO<Subscript>2</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>(MoO<Subscript>3</Subscript>)<Subscript>1–<Emphasis Type="Italic">n</Emphasis></Subscript> glasses

The thermal behavior of (TeO₂) _n (MoO₃)_1–n (n = 0.75, 0.85, 0.90) tellurite glasses has been studied by differential scanning calorimetry in the range from T = 300 to T = 850 K and heat capacity has been measured in the temperature range. The thermodynamic characteristics of the devitrification process and glassy state have been determined. The experimental data obtained have been used to evaluate the standard thermodynamic functions of the system in glassy and supercooled liquid states: heat capacity C _p °(T), enthalpy H°(T)–H°(320), entropy S°(T)–S°(320), and Gibbs function G°(T)–G°(320) in the temperature range 320–630 K. The composition dependences of the glass transition temperature and thermodynamic functions for the glasses have been obtained. The thermal and thermodynamic properties of the tellurite glasses have been compared to those of previously studied (TeO₂) _n (WO₃)_1–n and (TeO₂) _n (ZnO)_1–n glasses.     

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.     

High-temperature oxidation behaviour of Ti<Subscript>3</Subscript>Si<Subscript>(1−<Emphasis Type="Italic">x</Emphasis>)</Subscript>Al<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>C<Subscript>2</Subscript> in air

The oxidation behaviours of bulk Ti₃Si_(1−x)Al _x C₂ prepared by hot pressing were investigated. The results showed that the isothermal oxidation behaviour of Ti₃SiC₂ obeyed a parabolic law between 900 and 1100°C, and followed a two-step parabolic rate law between 1200°C and 1300°C. The cyclic oxidation behaviour of material is assumed to obey a three-step parabolic rate law at 1100°C and 1200°C. The calculated activation energy of isothermal oxidation is 101·43 kJ·mol⁻¹. The oxide layers consisted of a mass of α-Al₂O₃ and little TiO₂ and SiO₂ are observed on Ti₃SiC₂ as a dense and adhesive protect scale. The oxidation mechanism varies with the additive aluminum that greatly improves the oxidation resistance of Ti₃SiC₂.     

Antireflection properties of diamond-like carbon films on Cd<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Te (<Emphasis Type="Italic">x</Emphasis> ∼ 0.04) single crystals

The optical properties of diamond-like carbon (DLC) films obtained by plasmachemical deposition on Cd_{1 − x} Zn _x Te (x ∼ 0.04) single crystals have been studied by ellipsometry. The ellipsometric data have been interpreted within the framework of a three-layer model of the DLC film-semiconductor crystal refractory system with transition layers between the film and substrate. It is found that DLC films exhibit antireflection properties in this refractory system in the IR spectral range. It is established that the proposed antireflection film-substrate structure is stable with respect to thermal cycling and ultrasonic treatment.     

Thermal conductivity of Sn<Subscript>1–<Emphasis Type="Italic">x</Emphasis> </Subscript>Mn<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript>Te single crystals

The thermal conductivity of homogeneous crystalline Sn_1–xMn_xTe samples has been measured in the temperature range 90–305 K. We have determined their electron and lattice thermal conductivities and their thermal resistivity due to structural defects. The results demonstrate that the electron thermal conductivity reaches ~50% of the total thermal conductivity in some of the samples and that structural defects make an appreciable contribution to the thermal resistivity of the crystals.     

Thermoelectric performance of <Emphasis Type="Italic">n-type</Emphasis> (PbTe)<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>(CoTe)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> composite prepared by high pressure sintering method

Composites of nominal composition (PbTe)_1?x(CoTe) _x (x?=?0–0.18) were fabricated by high pressure (6 GPa) sintering (773 K) method. The thermoelectric performances were investigated in the temperature range of 293–773 K. The experimental results show that CoTe utilized as the secondary phase can remarkably enhance the TE properties of PbTe, of which the highest ZT value reaches 0.88 at 473 K when x?=?0.14. The enhancement of TE performance owes much to its high electric conductivity of CoTe. Meanwhile, the high pressure sintering (HPS) samples consist of nanoparticle, which significantly enhances the boundary scattering on carriers, decreases thermal conductivity, and increases Seebeck coefficient. All the results indicate that HPS method and the addition of CoTe-composite are effective methods to enhance the thermoelectric performance of PbTe as a potential TE material.     

Structure and Superconductivity of (MgB<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>C<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>0.97</Subscript>Cu<Subscript>0.03</Subscript>

A series of samples of (MgB_2−x C _x )_0.97Cu_0.03 (x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25) and MgB₂ were synthesized by a solid state reaction method. The structure, superconducting transition temperature and transport properties of the samples were studied by means of X-ray diffraction (XRD) and resistivity measurements. It is found that the c-axis of the lattice remains unchanged with increasing C doping, while the a-axis shows a small decrease. The T _c of the samples steadily decreases with increasing C doping. It is suggested that the chemical pressure effect plays a more important role influencing the normal state transport and T _c than the change of carrier concentration.     

Carrier mobility in Si<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> crystals

We have studied the 300-K carrier mobility in Czochralski-grown single crystals of undoped and heavily boron doped Si_{1 ? x} Ge _x (0 < x < 0.02) alloys. Comparison of our experimental data with theoretical predictions indicates that the Ge atoms in dilute Si_{1 ? x} Ge _x alloys do not act as neutral scattering centers. The carrier mobility related to the scattering by Ge atoms is governed by disorder (alloy) scattering. The carrier mobility in the boron-doped Si_{1 ? x} Ge _x alloys is much lower than that in the undoped alloys, depends very little on Ge content, and is governed by ionized impurity scattering.     

Magnetic Properties of CuTi<Subscript>2−2<Emphasis Type="Italic">x</Emphasis></Subscript>Cr<Subscript>2<Emphasis Type="Italic">x</Emphasis></Subscript>S<Subscript>4</Subscript> Materials

The magnetic properties of semi-conductor CuTi_2−2x Cr_2x S₄ systems have been studied. The nearest neighbour J ₁(x) and the next-neighbour super-exchange J ₂(x) interactions are evaluated by using the mean field theory for this spinel CuTi_2−2x Cr_2x S₄ system. The magnetic energy, the intraplanar and the interplanar interactions are deduced. The high-temperature series expansion (HTSE) combined with the Padé approximants method (PA) is applied to this spinel system to determinate the magnetic phase diagrams, i.e. T _C versus dilution x. The critical exponents associated with the magnetic susceptibility (γ) and with the correlation length (ν) are deduced in order phase.     

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.     

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.     

Thermal conductivity of Sn<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Nd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>S single crystals

The thermal conductivity of Sn_{1 − x} Nd _x S (x = 0, 0.001, 0.002) single crystals has been measured in the temperature range 80–840 K. The results have been used to evaluate the electronic and lattice components of the thermal conductivity. Both the electronic and lattice components are shown to decrease with increasing temperature and to increase with neodymium content.     

Mechanism of nanostructuring in fluorite-like Ca<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>La<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>F<Subscript>2 + <Emphasis Type="Italic">x</Emphasis></Subscript>

Nanostructuring in fluorite-like Ca_{1 ? x} La _x F_{2 + x} is shown to be associated with the precipitation of an CuAu-ordered phase. The shape of the precipitates is governed by the energetics of the {001} and {111} faces of tetragonal inclusions in highly anisotropic media and is nearly cuboctahedral. The misfit strain relaxes through the generation of twins, which nucleate along the intersection lines of {001} and {111} faces. The twins impede facial development and further growth and ordering of precipitates, thereby freezing the precipitation process in its initial stage. For this reason, the phase segregation is difficult to reveal, and Ca_{1 ? x} La _x F_{2 + x} crystals appear homogeneous.