Electronic peltier effect in Li<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Cu<Subscript>(2 − <Emphasis Type="Italic">x</Emphasis>) − δ</Subscript>S

Temperature dependences of the Peltier coefficient are studied in the temperature range of 300–700 K under variation of the composition of the Li _x Cu_{(2 − x) − δ}S samples. The obtained values of the Peltier coefficient of the Li_0.05Cu_{1.95 − δ}S samples with a different copper content are within the range of 0.1–0.4 J/A, which is somewhat higher than the similar parameters of bismuth telluride, the basic material of semiconductor coolers.     

Density-Functional Theory of Vibrations in Ni<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>V<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Clusters

We have performed the calculation of the vibrational frequencies, Fermi energy and binding energy for several clusters of Ni and vanadium atoms by using the first principles. The calculations are performed by using the density-functional theory in the local-density approximation with spin polarized orbitals. The calculation of vibrational frequencies shows that some of the clusters have positive vibrational frequencies which describe the oscillations of the stable clusters. The negative vibrational frequencies indicate that these clusters are instable with respect to these vibrations when no energy of this frequency is supplied. We find that for vanadium concentration less than 11.1% the clusters of Ni and V atoms are not stable. Hence ferromagnetism in Ni is predicted below 11.1% vanadium. We find the vibrational frequencies of several clusters for which the vanadium concentration is more than 11.1%. We are able to find a phase transition by use of quantum mechanics alone without the use of classical mechanical variables or thermodynamic variables such as temperature.     

Synthesis of (Ni<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Co<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>2</Subscript>P (0 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 0.65) substitution solid solution

The phosphides (Ni_{1 ? x} Co _x )₂P (0 ≤ x ≤ 0.65) crystallizing in the hexagonal system, space group P \(\bar 6\)2m, were synthesized in two steps starting from the continuous solid solution (Ni_{1 ? x} Co _x )₃(PO₄)₂ · 8H₂O. The initial phosphates were first completely dehydrated at 800°C and then reduced with hydrogen at 900–1000°C for 1–2 h.     

Potassium-conducting solid electrolytes in K<Subscript>1 − 2<Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>GaO<Subscript>2</Subscript> system

New solid electrolytes with a high conductivity by K⁺ ions in the K_{1 − 2x} Sr _x GaO₂ system are synthesized and studied. It is found that the introduction of Sr²⁺ ions into potassium monogallate leads to the formation of solid solutions with KGaO₂ structure in a wide range of additive concentration. These solid solutions exhibit a high conductivity; the conductivity increases monotonically with increasing concentration of strontium within the single-phase range. The electrical characteristics are related to the electrolyte structure. The results are compared with the earlier data for the gallate solid electrolytes with the additives of four-charged cations and the systems based on potassium monoferrite and monoaluminate.     

Ionic conduction of Li<Subscript>8 − 2<Emphasis Type="Italic">x</Emphasis></Subscript>Mg<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>ZrO<Subscript>6</Subscript> solid solutions

A boundary of existence of solid solutions in the Li_8−2x Mg _x ZrO₆ system is found to be 7 mol % MgO. The transport properties of Li_{8 − 2x} Mg _x ZrO₆ solid solutions (the electronic component of total conductivity, the temperature and concentration dependences of conductivity and activation energy) are studied. It is supposed that, for Li₈ZrO₆ phase and solid solution based on it, an abrupt change of conductivity in the temperature range from 663 to 713 K is caused by the transition of electrolyte into the superionic state.     

Thermal analysis of the Ce<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Tb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript> pigments

Compounds based on CeO₂ were synthesized as high-temperature environment-friendly inorganic pigments with interesting hues. The pigments have been synthesized by using the solid state reaction in the temperature range from 1,300 to 1,600 °C. The host lattice of these pigments is CeO₂ that is doped by terbium ions. The incorporation of doped ions provides interesting orange colours after application into ceramic glaze. The goal was to develop conditions for the synthesis of these compounds and to determine the influence of calcination temperature on their colouring effects. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments. The pigments were also evaluated from the standpoint of their structure and particle sizes.     

Potassium–conducting K<Subscript>1 − 2<Emphasis Type="Italic">x</Emphasis></Subscript>Pb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>GaO<Subscript>2</Subscript> solid electrolytes

Solid electrolytes with potassium-cation conductivity in the K_{1 − 2x} Pb _x GaO₂ system were synthesized and studied. It was found that solid solutions based on potassium monogallate are formed in a wide range of compositions. They contain vacancies in the potassium sublattice that provide for high conductivity of electrolytes. The relationship is considered between electric characteristics of solid electrolytes and the composition and structure of solid solutions. The results are compared to the earlier obtained data for similar solid electrolytes based on potassium monoaluminate and monoferrite.     

Electrotransport Properties of Ceramics Based on Bi<Subscript>4</Subscript>V<Subscript>2 − <Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript>x</Subscript>O<Subscript>11 − <Emphasis Type="Italic">x</Emphasis></Subscript>

Conditions for the formation of single-phase compounds in the synthesis of solid solutions Bi₄V_{2 − x} Fe_xO_{11 − x} are studied. The sequence of phase transitions is determined. Parameters of unit cells of solid solutions are determined. The net conductance as a function of temperature and composition is studied.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 607–609.Original Russian Text Copyright © 2005 by Emel’yanova, Buyanova, Zhukovskii.     

Transport and thermal characteristics of Cs<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Rb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>H<Subscript>2</Subscript>PO<Subscript>4</Subscript>

The transport and thermal properties of Cs_{1 − x} Rb _x H₂PO₄ in a wide range of compositions were studied. The binary salts Cs_{1 − x} Rb _x H₂PO₄ (x = 0–0.9) contain solid solutions with a structure of CsH₂PO₄. The binary salts were synthesized by mechanically mixing the starting components and growing crystals by isothermal evaporation from aqueous solutions. The properties of Cs_{1 − x} Rb _x H₂PO₄ salts obtained by different procedures were found to differ considerably. At higher rubidium contents in compounds obtained by mechanical mixing, the superionic transition temperature rose insignificantly, the high-temperature phase conductivity decreased twofold, the low-temperature conductivity increased within the limits of the order of magnitude, and the system of hydrogen bonds was slightly weakened. In Cs_{1 − x} Rb _x H₂PO₄ crystals grown from solutions, the temperature of the superionic transition decreased along with its slowing down, and the low-temperature conductivity increased by more than three orders of magnitude because of the higher contents of residual acid aqueous centers in the structure of the salt. These systems are characterized by increased thermal stability.     

CdSe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>S<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>/CdS-cosensitized 3D TiO<Subscript>2</Subscript> hierarchical nanostructures for efficient energy conversion

Three-dimensional TiO₂ hierarchical nanostructures (3D-TiO₂-HNs) containing TiO₂ nanotrees and nest-like hollow spheres were synthesized and used as backbones for CdSe _x S_1?x quantum dot (QD) loading. These CdSe _x S_1?x QD-sensitized 3D-TiO₂-HNs were then used as photoelectrodes in the preparation of quantum-dot-sensitized solar cells. As revealed by TEM images, the highly porous 3D-TiO₂-HNs represent an excellent framework on which to deposit a large number of CdSe _x S_1?x QDs in order to form homogeneous and compact CdSe _x S_1?x -sensitized layers in photoelectrodes using a spin-assisted successive ionic layer adsorption and reaction method (spin-SILAR). Following careful adjustment of the molar ratio of Se^2? to S^2?, the number of spin-SILAR cycles, and the thickness of the CdS passivation layer used, the best-performing QDSC was shown to yield a short-circuit current density of 18.22 mA cm^?2, an open-circuit voltage of 0.520 V, a fill factor of 0.510, and a power conversion efficiency of 4.83%. This high performance is possible because the device is able to absorb a relatively broad range of wavelengths and because charge recombination is suppressed in the device.     

TiO<Subscript>2</Subscript>/TiO<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>N<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> nanocomposite and its acetaldehyde photodecomposition ability

Nitrogen-doped titania was coupled with the commercial titania nanoparticles by mechanical milling in liquid medium. The as-prepared nanocomposites (TiO₂/TiO_2−x N _y ) were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) specific surface area, UV–Vis spectroscopy, chemiluminescence, and acetaldehyde decomposition activity techniques. When a small amount of nitrogen-doped titania was added into the commercial titania, higher intensity and longer lifetime of ¹O₂ was observed, and the photocatalytic activity was efficiently improved. The TiO_2−x N _y acts as the acceptor of photoinduced holes. The recombination of the electron-hole was effectively depressed by the heterogeneous electron transfer. This could be an effective way to obtain highly active photocatalysts.     

Synthesis and electrochemical evaluation of La<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>MnO<Subscript>3</Subscript> catalysts for zinc-air batteries

La_1-x Sr _x MnO₃ (x?=?0.1～0.4) catalysts for primary and rechargeable zinc-air batteries have been successfully synthesized by the citrate method and their electrochemical properties measured. The materials can catalyze both ORR and OER, and the one with ideal composition of La_0.8Sr_0.2MnO₃ catalyst exhibits the highest catalytic activity and durability in alkaline medium. The resulting primary zinc-air cell shows a peak power density of 146 mW cm^?2 at 235 mA cm^?2. The secondary cell exhibits a charge-discharge voltage gap of 1.0 V at 10 mA cm^?2, which is highly stable over many charge-discharge cycles.     

Sol-Gel Synthesis and Properties of Y<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Ba<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>FeO<Subscript>3</Subscript> Nanocrystals

The sol-gel method was used to prepare Y_1–xBa_xFeO₃ (x = 0, 0.05, 0.1, 0.15, 0.2) nanocrystals. The influence of the dopant content on the particle size and magnetic properties of yttrium ferrite was examined.     

Resonant photoemission and absorption spectroscopy study of the Cr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ti<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Se<Subscript>2</Subscript> electronic structure

Solid solutions of 1T-Cr _x Ti_1?x Se₂ (x = 0?0.83) were synthesized for the first time. To study the electronic structure of Cr _x Ti_1?x Se₂ monocrystals, photoemission spectra of core levels, resonance spectra of valence bands, and absorption spectra of Ti and Cr were obtained. Titanium and chromium atoms were found to have the oxidation state 4+ and 3+, which is supported by atomic multiplet calculations for Ti and Cr in the octahedral environment. According to calculation of the local density of chromium electronic states, the Cr3d electrons are spin-polarized, and the density of chromium states is of half-metal nature. The calculation agrees well with the experimental data.     

Transport and structural properties of compounds (1 − <Emphasis Type="Italic">x</Emphasis>)CsHSO<Subscript>4</Subscript>-<Emphasis Type="Italic">x</Emphasis>KH<Subscript>2</Subscript>PO<Subscript>4</Subscript>

The homogeneous substitution of cations (K⁺) and anions (H₂PO₄⁻) for CsHSO₄ is performed. The dependences of protonic conductivity and structure of (1 − x)CsHSO₄-xKH₂PO₄ (x = 0.05–0.9) compounds on the composition are studied. It is found that the introduction of KH₂PO₄ leads to the formation of a new highly conductive phase. At small amounts of introduced KH₂PO₄ (x = 0.05), a mixed salt forms; its low-temperature conductivity is by more than two orders of magnitude higher than that of the source salts. The thermal behavior of mixed salt (1 − x)CsHSO₄-xKH₂PO₄ of various compositions and the peculiarities of crystal structure are studied. The structural parameters of the salt at x = 0.05–0.5 are close to those of Cs₃(HSO₄)₂(H₂PO₄). At higher x, another phase forms, whose structure has yet to be determined. The thermal stability of the salt decreases with increasing fraction of KH₂PO₄ introduced. The conductivity of the composites based on the mixed salt and silicon dioxide (1 − y){xKH₂PO₄-(1 − x)CsHSO₄}-ySiO₂ (x = 0.05, 0.1; y = 0.1–0.7) is studied. It is shown that, in the low-temperature range, the conductivity of composite systems increases within an order of magnitude, passes through a maximum, and, then, decreases at y > 0.5 due to the percolation effect.     

Hydrothermal synthesis of Zn<Subscript>2</Subscript>Sn<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ti<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>4</Subscript> as anode material for lithium-ion batteries

A novel electrode material, Zn₂Sn_{1 − x} Ti _x O₄ (x = 0 and 0.1), which is superior in its electrochemical characteristics to the reverse spinel Zn₂SnO₄, is synthesized by hydrothermal method. The admixture of TiO₂ levels out the volume expanding caused by the Li-Sn and Li-Zn alloy formation thus improving the material’s cyclability.     

Chemical etching of Cd<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Te solid solution single crystals with iodine solutions in methanol

Chemical etching of Cd_{1 ? x} Mn _x Te (0.04 < x < 0.5) solid solution (ss) single crystals in I₂ + CH₃OH etching mixtures was studied. Concentration and kinetic curves of etching rates were plotted. As the manganese concentration of the solid solution increases, the rates of their etching by iodine-methanol etchants increase, too. The etchant compositions and chemical-dynamic polishing protocols for Cd_{1 ? x} Mn _x Te single crystals were optimized.     

Mixed silicon–germanium nanocrystals: a detailed study of Si<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript>47−<Emphasis Type="Italic">x</Emphasis></Subscript>:H

Mixed SiGe:H nanocrystals have been studied within the framework of Density Functional Theory. (DFT) using the hybrid non-local exchange-correlation functional of Becke, Lee, Parr and Yang (B3LYP). In addition to ground-state DFT/B3LYP calculations, excited-state calculations for the determination of the optical absorption spectrum have been performed employing the time-dependent density functional theory (TDDFT). In order to fully investigate the substitution of Si by Ge, on structural, cohesive, electronic and optical properties, we have used the Si _x Ge_47−x :H nanocrystal, as a representative medium size nanosystem. Our results show that the optical gap depends not only on the relative concentrations of silicon, germanium and hydrogen, but also on the relative position of the silicon and germanium shells relative to the surface of the nanocrystal. This is also true for the structural, cohesive and electronic properties. This dependence allows for the possibility of electronic and optical gap engineering.     

Aqueous germanate solution,alternative sol–gel precursor for preparation of Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript> diluted magnetic semiconductors

The solids content and gelation time of aqueous germanate solution were examined in this work. Samples of 5, 10 and 20 mol% Mn doped Ge were prepared by using the aqueous germanate solution as a liquid Ge precursor. No second phase such as Mn₅Ge₃ was detected in the 5 and 10 mol% Mn doped samples, implying that Mn ions were uniformly diluted into the Ge host matrix. The 5 and 10 mol% Mn-doped Ge samples exhibit room-temperature ferromagnetic behaviors that are likely originated from the RKKY (Ruderman–Kittel–Kasuya–Yosida)-like interaction between the localized Mn ions in the Ge matrix. Therefore, the aqueous germanate solution can be an alternative sol–gel precursor for preparation of the Mn _x Ge_1−x diluted magnetic semiconductors (DMSs).