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.     

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.     

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.     

High-temperature ion transport in La<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>FeO<Subscript>3−δ</Subscript>

The conductivity of the entire solid solution La_1–xSr_xFeO_3–, where x=0.2, 0.4, 0.5, 0.7 and 0.9, in the oxygen partial pressure range 10^–19 to 0.5 atm and temperatures between 750 and 950 °C is reported. The analysis of the isothermal pressure dependences of the conductivity reveal that the lanthanum-strontium ferrites can be characterized as mixed ion-electron conductors in the low-oxygen pressure/high-oxygen deficiency limit. The partial contribution to conductivity from oxygen ions increases with strontium content and attains a maximal value at x=0.5. Further increase in doping results in the development of oxygen vacancy ordering phenomena and deterioration of the conducting properties.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003     

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.     

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.     

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.     

Magnetic diagram of CuCr<Subscript>2 – <Emphasis Type="Italic">x</Emphasis></Subscript>Sb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Sе<Subscript>4</Subscript> solid solutions

Temperature-dependent magnetization was measured for CuCr_2–x Sb _x Sе₄ solid solutions in the range 300–5 K in a weak field (50 Oe) and a strong field (10 kOe) and in an ac magnetic field having a frequency of 100–10000 Hz and an amplitude of Н = 1 Oe. The type and character of magnetic transitions under investigation in the system were determined, and its magnetic phase diagram was constructed.     

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.     

Fast evaluation of molecular auxiliary functions <Emphasis Type="Italic">A</Emphasis><Subscript>α</Subscript> and <Emphasis Type="Italic">B</Emphasis><Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> by analytical relations

Analytical relations through the initial values are derived for the molecular auxiliary functions A _α (x) and B _n (x), where α =n+ɛ, 0⩽ ɛ < 1 and n=0,1,2,.... These relations are useful in the fast calculation of multicenter molecular integrals over integer and noninteger n Slater type orbitals. It is shown that the formulas obtained are numerically stable for all values of n,ɛ and x.PACS No: 31.15.+q, 31.20.EjAMS subject classification: 81-V55, 81-V45     

Magnetic properties of CuCr<Subscript>2–<Emphasis Type="Italic">х</Emphasis></Subscript>Sb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Se<Subscript>4</Subscript> (<Emphasis Type="Italic">х</Emphasis> = 0–0.5) solid solutions

Magnetic properties of spinel solid solutions CuCr_2–х Sb _x Se₄ (х = 0–0.5) were measured in the temperature range 5–300 K in a constant (50 Oe and 10 kOe) magnetic field. The results are interpreted in terms of the ionic model suggested earlier for CuCr₂Х₄ compounds.     

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.     

Anodic Electrocatalysts for Fuel Cells Based on Pt/Ti<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Ru<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript>

The electrocatalytic activity of materials in the 10% Pt/Ti_1–xRu _x O_2–δ system, where x = 0–0.3 (0 ≤ Ru ≤ 30 mol %), in the reactions of hydrogen electrooxidation in the presence of CO is studied in the liquid three-electrode cell and a model of fuel cell. It is shown that the tolerance of the electrocatalysts towards CO is determined by the crystal structure of the support: the support with the rutile structure provides a higher rate of CO desorption than the support with the anatase structure. The potential of the onset of CO oxidation decreases with increasing concentration of dopant in the support from 650 mV for 10% Pt/TiO₂ to 480 mV (NHE) for 10% Pt/Ti_0.91Ru_0.09O_2–δ (rutile). The use of these materials as the anodic catalysts of fuel cell operating with hydrogen containing 30 ppm CO enabled us to obtain a current density by 7 times higher as compared with the 20% PtRu/C E-Tec catalysts.     

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.     

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.     

Formation of Nd<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Bi<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>FeO<Subscript>3</Subscript> Nanocrystals under Conditions of Glycine-Nitrate Synthesis

Nd_1–xBi_xFeO₃ nanocrystals with crystallite size 30?60 nm have been prepared under conditions of glycine–nitrate burning. Single-phase Nd_1–xBi_xFeO₃ nanocrystals are formed over the entire studied concentrations range if the glycine–nitrate synthesis is performed in excess of the oxidizer. Under these conditions, a continuous range of the Nd_1–xBi_xFeO₃ solid solutions (0 ≤ х ≤ 0.75) crystallized in the rhombic system (space group Pbnm) are formed without crystallization of the burning intermediates. The Nd_1–xBi_xFeO₃ solid solutions (х = 0.775, 0.8) crystallize in the rhombic system (space group Pbаm).     

Production and characteristics of substituted lanthanum niobate LaNb<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>W<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>4 + δ</Subscript>

Solid solutions LaNb_1–x W _x O_{4 + δ} (x = 0.02–0.10, Δx = 0.02) were investigated, which crystallize in the monoclinic system (space group I2/c) at room temperature and undergo a phase transition into the tetragonal modification with increasing temperature. The stability of various modifications was analyzed by high-temperature X-ray powder diffraction analysis. The electrical conductivity of sintered samples was studied by impedance spectroscopy. Insertion of tungsten into the niobium sublattice leads to an increase in the conductivity of the solid solutions.