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.     

The thermovoltaic effect in variband solid solution Si<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> (0 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 1)

The thermovoltaic effect in films of variband solid solution Si_1–x Ge _x (0 ≤ x ≤ 1) has been observed for the first time. The samples comprised n-Si–p-Si_1–x Ge _x (0 ≤ x ≤ 1) heterostructures grown by liquid phase epitaxy. An electromotive force within 0.05–0.3 mV and a current of 0.0025–0.0035 μA appeared on heating samples in a temperature range from 40 to 250°C.     

Structure of CN<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> films (0 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 0.5) deposited by arc sputtering of graphite

The structure of a-C and CN _x coatings 1–3 μ thick deposited on metal substrates by arc-pulse sputtering of graphite target in nitrogen background at P = (10^?2 ?5) Pa was studied by transmission electron microscopy and scanning electron microscopy. Concentration and depth distribution of nitrogen in CN _x depend on progressive saturation of graphite target. Nitrogen-free coatings (x = 0) consist of amorphous matrix with multiwalled nanotubes. Structure of carbon nitride coatings depends on nitrogen concentration. Over the range of C_N/C_C < 0.15 and C_N/C_C > 0.4 CN _x coatings are amorphous. The structure of CN_0.15<x<0.4 is a mixture of two types of amorphous domains, one of which is decorated by microcrystalline inclusions. The same structured inclusions were found on graphite target modified by electric arc. The obtained results allow understanding the dependence of the CN_0≤x≤0.5 coatings properties on nitrogen concentration.     

Effect of high-pressure high-temperature processing on the phase composition of Mn<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>Cr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Sb (0 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 1) alloys

High-pressure high-temperature processing (p = 7 GPa, T = 2300 K) has been shown to alter the phase composition of Mn_2?x Cr _x Sb alloys, resulting in a two-phase state: Mn₃Sb (sp. gr. Pm3m, no. 221) and a hexagonal phase of variable composition (sp. gr. P6₃/mmc, no. 194). With increasing chromium concentration, the content of the hexagonal phase increases, while that of the cubic phase drops. In addition, the occupancy of the bipyramidal interstitial sites in the hexagonal phase increases, reaching a maximum in the single-phase alloy MnCrSb (Ni₂In structure).     

A Modal of Twin Domains in YBa2(Cu1−<Emphasis Type="Italic">x</Emphasis>Co<Emphasis Type="Italic">x</Emphasis>)3O<Emphasis Type="Italic">y</Emphasis>

The existence of twin domains in YBa₂(Cu_1?xCo _x )₃O _y samples was confirmed by many experiments. However, the physical picture of the twin domains has not been reported up to now. By analyzing oxygen content, Cu and Co valences, and Co coordination in those samples, we propose a domain model, which consists of two pairs of parallel zigzag Co-O chains surrounding orthorhombic cells, one along (110) direction and the other along (110) direction. The zigzag Co-O chains are the twin walls, with neighboring walls perpendicular and the opposite ones parallel. The distance between parallel walls (i.e., zigzag Co-O chains) depends upon Co concentration of sample. The twin domain model predicts the geometry, size, and absence of systematic symmetry of the domains. The model also predicts the modulation periodicity of electron diffraction patterns, which depends on Co concentration. All the predictions by the model agree well with the experimental results reported in literatures. Furthermore, the model indicates the possible existence of two domains, which have incommensurable modulation periodicity.     

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).     

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.     

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.     

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.     

Properties of amorphous Si<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>:H (<Emphasis Type="Italic">x</Emphasis> = 0−1) films

Plasma deposition has been used to grow Si_1?x Ge _x :H(x= 0 ? 1) films, undoped and doped with PH₃ or B₂H₆, for p-i-n solar cells and other optoelectronic applications. The optical, electrical, and photoelectric properties of the films have been studied at constant hydrogenation and doping levels. The films deposited under appropriate conditions are amorphous, and three-layer solar cells fabricated from such films offer an efficiency of 9.5% at an illumination of 100 mW/cm². The photoresponse of the a-Si_{1 ? x} Ge _x :H films strongly depends on Ge content. The hydrogen concentration in the films was controlled by varying the gas phase composition and was determined from the IR absorption in the films.     

Inhomogeneous magnetic states in Mn<Subscript>2 − <Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Sb (0.6 ≤ x ≤ 1.0) solid solutions

Mn_{2 ? x} Zn _x Sb (0.6 ≤ x ≤ 1.0) solid solutions are shown to undergo magnetic phase separation (coexistence of two magnetic phases in a structurally homogeneous material) using a combination of characterization techniques (magnetometry, X-ray diffraction, neutron diffraction, Mössbauer spectroscopy, and resistivity measurements). A model is presented for the coexistence of two magnetic phases in the two-sublattice ferrimagnet Mn₂Sb diamagnetically diluted with zinc.     

Relaxation phenomena in EDAMn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Cd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Cl<Subscript>4</Subscript> perovskite; 0≤ <Emphasis Type="Italic">x</Emphasis> ≤ 1 perovskite

The electrical properties measurements were carried out for the complex (CH₂)₂Mn_1–xCd_xCl₄, 0.0 x 1.0 at different temperatures as a function of frequency (100–1000 kHz). Four transition points were obtained for x = 0.5, which were assigned as thermochroism, interlayer exchange interaction, order-disorder and chain melting transition. The presence of more than one straight line in the conductivity data clarifies the presence of more than one conduction mechanism, and the calculated values of the activation energy indicate the semiconducting characteristics of the investigated complexes. The values of the relaxation time depend on Cd-content as well as the heating temperature. The expected critical concentration at x = 0.5 agrees well with the percolation theory of Mont-Carlo group. The IR spectra indicate that, the force constant of the bonds and the atomic mass vibration are affected by Cd-content.     

Properties of YBaCuFe<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ni<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>5</Subscript> (0 < <Emphasis Type="Italic">x</Emphasis> ≤ 0.3) solid solutions

YBaCuFe_{1 – x}Ni_xO₅ solid solutions are shown to exist for x 0.3. Data are presented on the lattice parameters, thermal stability, thermal expansion, electrical conductivity, thermoelectric power, magnetic susceptibility, and dielectric properties of the solid solutions. Ni substitution for Fe notably increases the electrical conductivity of the solid solutions, reduces their thermoelectric power and thermal expansion, and shifts the antiferromagnetic—paramagnetic phase transition and dielectric anomalies in YBaCuFe_{1 – x}Ni_xO₅ to lower temperatures.Translated from Neorganicheskie Materialy, Vol. 40, No. 12, 2004, pp. 1515–1519.Original Russian Text Copyright © 2004 by Chizhova, Klyndyuk, Bashkirov, Petrov, Makhnach.     

<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.     

Spin Gap Characteristic of Y(Ba1−<Emphasis Type="Italic">x</Emphasis>Gd<Emphasis Type="Italic">x</Emphasis>)2Cu3O7−δ

Y(Ba_1?xGd _x )₂Cu₃O_7?δ compounds with x = 0 ～ 0.15 are prepared using the solid reaction technique. With structure analysis by Rietveld refinement of x-ray diffraction, we find that Gd³⁺ ions prefer to occupy Y sites within lighter doping x ≤ 0.08 due to ion size effects, then begin partially to occupy Ba sites with doping content increasing, which gives vital influence on superconductivity and spin-gap properties. The magnetic doping effects of Gd³⁺ ions on spin-gap properties are investigated in detail by contrast of the distinguished behaviors between T* and T_c, indicating that spin-gap temperature is not completely determined by the carrier density, but strongly dependent on the strength of interplane antiferromagnetic coupling. Finally, we propose an expression of in-plane resistivity dependent on the maximal width of spin-gap Δ₀ to derive their values for different samples, which almost keep constant with the increase of Gd doping contents.     

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.     

Good electrical performances and impedance analysis of (1 − <Emphasis Type="Italic">x</Emphasis>)KNN–<Emphasis Type="Italic">x</Emphasis>BMM lead-free ceramics

(1 ? x)(K_0.5Na_0.5)NbO₃–xBi(Mg_0.75Mo_0.25)O₃ [(1 ? x)KNN–xBMM] (x?=?0.005, 0.01, 0.02) ceramics were prepared via a solid-state reaction method. X-ray diffraction patterns (XRD) and Raman spectrum showed that a solid solution was formed between the BMM and KNN, which improved the electrical properties of KNN. With increasing the BMM content, the grain firstly increased and then decreased. When x?=?0.01, the ceramics exhibited the optimized microstructure, indicating that there exits an optimal doping component. Temperature dependence of relative permittivity also increases firstly and then decreases. The relative permittivity (ε_r) of ~?1418 in stabilization zone, ε_max?~?4861 at the Curie temperature T _C ~ 394 °C, good temperature stability ?ε/ε_123 °C?≤?±?15% from 123 °C to 348 °C, and the dielectric loss tanδ?≤?0.036 from 109 to 348 °C were obtained for 0.99KNN-0.01BMM ceramics. Conductivity behavior of the (1 ? x)KNN–xBMM was investigated as a function of temperature from 420 to 520 °C and frequency from 40 to 106 Hz, showing that the basic mechanisms of conduction and relaxation processes were thermally activated, and oxygen vacancies were the possible ionic charge transport carriers at higher temperatures.     

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.