Adsorption, electrophysical, and optical studies of the surface of solid solutions and the binary components of the InSb-ZnTe system

Piezoquartz microweighing, surface electroconductivity measurements, and IR and Raman spectroscopies were used to study the mechanism and regularities of the interaction of carbon monoxide, ammonia, and oxygen, gases of different electronic natures encountered in the environment and various technological processes, with the surface of solid solutions and the binary compounds of the InSb-ZnTe system. An analysis of the results with the use of the acid-base and other physicochemical characteristics of the adsorbents and of the electronic properties of the adsorbate molecules showed that the values of adsorption of the gases lie within α = 10⁻⁵−10⁻³ mol/m². It was demonstrated that, at temperatures above 293 K, the adsorption of CO and NH₃ occurs by the donor-acceptor mechanism, whereas oxygen is adsorbed through the ion-radical mechanism, with the predominant participation of coordinatively unsaturated metal atoms and vacancy defects, respectively. It was revealed that the acid-base, adsorption, electrophysical, and optical properties vary similarly with changing composition of the system, a behavior that suggests the same origin of adsorption sites and inherent surface states and makes it possible to predict the adsorption activity of a surface on the basis of its acid-base properties and the properties of the binary compounds and constituent elements. Similarities and distinctions in the behavior of (InSb) _x (ZnTe)_{1 − x} solid solutions and the binary compounds (InSb and ZnTe) were identified. Specific features of solid solutions, as multicomponent systems, are that adsorption on them is energetically more favorable, especially well pronounced in the acid-base characteristic-composition and adsorption characteristic-composition diagrams. Such diagrams made it possible to determine the solid solution most active with respect to ammonia, (InSb)_0.95(ZnTe)_0.05, which was used to make a selective high-sensitivity gas sensor.     

Bulk and surface properties of ZnTe–ZnS system semiconductors

Physicochemical studies of a new ZnTe–ZnS semiconductor system are conducted. It is found that at certain ratios of binary components, substitutional solid solutions with a cubic sphalerite structure are formed in this system. Interrelated laws governing changes in the bulk (crystal chemical, structural) and surface (acid–base) properties with varying system composition are identified. It is assumed they can be attributed to the nature of the active (acid–base) sites. The presented data, observed patterns, and an interpretation of them are used not only to confirm earlier proposed mechanisms of atomic–molecular interaction on diamond-like semiconductors, but to search for promising materials for use in highly sensitive selective sensors for environmental and medical purposes as well.     

Metal dilution effects on the spin-crossover properties of the three-dimensional coordination polymer Fe(pyrazine)[Pt(CN)4

The 1A1 left arrow over right arrow 5T2 spin transition has been investigated in the solid solutions of Fe(x)M(1-x)(pyrazine)[Pt(CN)4] (M = Ni or Co, 0 < or = x < or = 1) having a three-dimensional polynuclear structure. Both Ni and Co dilutions tend to decrease the hysteresis width and smooth the transition curves. The enthalpy (entropy) change associated with the spin transition was found to decrease from 26 kJ mol(-1) (84 J K(-1) mol(-1)) for x = 1 to 12 kJ mol(-1) (47 J K(-1) mol(-1)) for 47% Co dilution and to 15 kJ mol(-1) (54 J K(-1) mol(-1)) for 59% Ni dilution. Raman spectroscopy revealed a mixed one- and two-mode behavior in the solid solutions. For the first time, a correlation between vibrational frequencies exhibiting one-mode behavior and the entropy change, which drives the spin crossover, is established.     

The adsorption of gases on the surface of solid solutions and binary compounds of the GaSb-ZnTe system

The adsorption of ammonia, carbon monoxide, and oxygen on solid solution and binary compound films of the GaSb-ZnTe system was studied. The mechanism of adsorption and rules governing adsorption processes depending on adsorption conditions and system composition were determined by analyzing adsorption isobars, equilibrium and kinetic isotherms, the thermodynamic and kinetic characteristics of adsorption, and the electronic nature of adsorbate molecules. The behavior of (GaSb)_x(ZnTe)_1?x solid solutions was similar to that of binary compounds (GaSb and ZnTe) and had special features characteristic of multicomponent systems. The latter manifested themselves by the presence of extrema in adsorption characteristic-composition diagrams. The use of such diagrams allowed us to identify system components most active with respect to NH₃, CO, and O₂ and use them to create high-sensitivity and selectivity sensors.     

Phase diagram of the (CuInTe2)1−x(2ZnTe)x system and crystal growth of CuZn2InTe4 from zinc chloride flux

The phase diagram of the system (CuInTe₂)_1?x(2ZnTe)_x has been investigated by microstructure, DTA, and X-ray examinations. It has been found that CuInTe₂ and ZnTe form, at elevated temperatures, a continuous series of zincblende solid solutions. The boundaries of the solid-phase fields have been established: At room temperature, the tetragonal chalcopyrite phase α is stable up to about the x = 0.10 composition and is followed by a two-phase region (α + β), extending from x = 0.10 to x = 0.33 composition, and by a region x ? 0.33 with the cubic zincblende β structure. Using the flux growth technique with ZnCl₂ as solvent, single crystals of the CuZn₂InTe₄ composition (x = 0.50), closely related to the diamond lattice, have been obtained.     

MgS-FeS phase diagram

The MgS-FeS system has a peritectic phase diagram with limited terminal solid solutions. The maximal solubility in FeS is reached at the peritectic point and is 2 mol % MgS at 1470 K. The extent of the MgS-based solid solution is 25 mol % MgS at 1470 K, 42 mol % MgS at 1170 K, and 65 mol % MgS at 770 K. The unit cell parameter of the cubic MgS phase (a NaCl-type structure) varies from 0.5196 nm (MgS) to 0.5164 nm (65 mol % MgS, 770 K) and 0.5127 nm (42 mol % MgS, 1170 K). The microhardness varies from 2600 to 3040 MPa. The iron ions in the solid solution are in a low-spin state.     

Hydrothermal synthesis of tungsten molybdenum mixed oxides

The phase composition, particle size, and morphology of ultrafine products recovered as a result of hydrothermal treatment of precursor solutions were studied. The precursor solutions were prepared by ion exchange and contained various proportions of tungsten and molybdenum. When tungsten percentages in the precursor solution were 20–95 mol %, the major synthesis product was a mixed oxide (substitutional solid solution (W, Mo)O₃ · 1/3H₂O based on the structure of crystal hydrate WO₃ · 1/3H₂O). When the tungsten percentage was 5 mol %, the product was (W, Mo)O₃ solid solution with the structure of orthorhombic MoO₃. Particle shapes and sizes (ranging from 20 to 8 000 nm) were dictated by the proportion between tungsten and molybdenum compounds in the precursor solution and by the method used to prepare the precursor.     

Thiourea complexes in synthesis of Cd1 ? xZnxS solid solutions

Solid solutions of the CdS-ZnS system deposited as polycrystalline films by aerosol pyrolysis from aqueous solutions of cadmium and zinc thiourea complexes have been studied. The phase composition and solid-phase solubility are dictated by the nature of initial complexes. From solutions of [M(thio)₂(CH₃COO)₂] complexes, sphalerite sulfides are precipitated, which form a continuous solid solution s-Cd_1−x Zn _x S, whereas the use of the [M(thio)₂Cl₂] precursor leads to crystallization of the wurtzite w-Cd_1−x Zn _x S solid solution based on CdS (the homogeneity range 0–20 mol % ZnS) and the s-Cd_1−x Zn _x S solid solution based on zinc sulfide (50–100 mol % ZnS). The structure of the solid phase in the sulfide system is attributed to the specific features of the stereochemistry of complex precursors.     

Mesomorphic and dielectric properties of the p-n-hexyloxybenzoic acid-p-n-heptyloxybenzoic acid liquid crystal system

Thep-n-hexyloxybenzoic acid (I)-p-n-heptyloxybenzoic acid (II) system was investigated by thermal and X-ray phase analyses and dielcometry. Solid solutions of three types were found in the low-temperature region of the system, namely, solid solution based on I (up to 15 mol % II); solid solution based on a compound with the equimolar ratio of the components (γ); and solid solution based on II (>15 mol % II). The range of the two-phase equilibrium (N + I) was 2°–4°; a continuous nematic solution (N) formed in the system. The temperature and composition dependences of dielectric anisotropy Δ? were characterized. The γ compound showed negative dielectric anisotropy, Δ? = ?1.4, which was constant over the whole temperature range of the nematic phase.     

Ternary reciprocal systems Na,K||BO<Subscript>2</Subscript>,CO<Subscript>3</Subscript> and Na,K||BO<Subscript>2</Subscript>,Cl

The phase diagrams of the ternary reciprocal systems Na,K||BO₂,CO₃ and Na,K||BO₂,Cl were studied for the first time by a calculation-experimental method and by differential thermal analysis. Analytical models of phase equilibrium states were derived, and the coordinates of eutectics were found to be (680°C, 32 mol % NaBO₂, 68 mol % KCl) and (648°C, 9 mol % NaBO₂, 45.5 mol % NaCl, 45.5 mol % KCl). Binary solid solutions based on metaborates and carbonates of sodium and potassium were shown to be stable. The possibility of synthesizing tungsten oxide bronzes in a eutectic melt in the ternary system NaBO₂–NaCl–КCl was revealed.     

Kinetics of Glucose Mutarotation in Aqueous Urea Solutions

Kinetics of glucose mutarotation in water-urea mixtures with urea concentrations of 0-15 mol % was studied in the temperature range 283-308 K. It was found for the first time that the rate of mutarotation increases with increasing concentration of urea in water. It was established that urea molecules along with water molecules affect directly the reaction rate via specific solvation. The fact that the activation parameters are almost independent of the concentration of urea was explained in terms of preservation of the structure of the solutions in the composition range studied.     

掺杂正八面体AgBr乳剂介电频谱的研究——Cd2+、Br-离子的影响

测定了单分散正八面体AgBr乳剂中加入不同量CdBr₂和KBr以后的介电吸收频谱。发现Cd²⁺离子的表面掺杂使正八面体AgBr乳剂的介电吸收峰向低频方向位移。这种变化在CdBr₂的加入量为0—2×10^-2mol/mol AgBr范围内尤为明显。说明掺杂Cd²⁺使正八面体AgBr乳剂中AgBr微晶的介电电导率σ₂显著下降。能进入AgBr微晶表面层晶格中的Cd²⁺离子的数量不仅与乳剂中Cd²⁺离子的浓度有关,而且与乳剂中的Br^-离子浓度有关。通过简单的水洗,可以将掺杂的Cd²⁺大部分除去。水洗后,样品的介电吸收峰又向高频方向回移。在本实验条件下,Cd²⁺离子掺杂的这种“可逆性”表明进入AgBr微晶中的Cd²⁺离子主要是处在AgBr微晶的表面层内。样品介电吸收峰频率位置的这种可逆变化表明:非均匀电介质中的界面极化效应在保持连续相不变时,受分散相颗粒表面层物质的组成和结构的影响很大。     

盐酸后处理制备高效制氢光催化剂Zn2In2S5

采用水热法制备了ZnIn₂S₄固溶体, 并通过用盐酸对其进行后处理获得了系列Zn_mIn₂S_m+3(m≥2, 整数)固溶体. 通过X射线衍射(XRD)、 扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 X射线光电子能谱(XPS)、 紫外-可见漫反射光谱(UV-Vis DRS)、 荧光光谱(PL)和电化学测试对催化剂的组成、 结构和性能进行了表征. 研究了系列固溶体可见光光催化制氢活性. 结果表明, ZnIn₂S₄固溶体经0.5 mol/L HCl处理后能转化为Zn₂In₂S₅固溶体, 其制氢活性为ZnIn₂S₄固溶体的2.2倍, 并且具有良好的稳定性.     

Formation of solid solutions in the CdSe–PbSe system under the action of high pressures and temperatures

A method was proposed for producing solid solutions in the CdSe–PbSe systems, which is based on heat and high pressure treatment. X-ray powder diffraction analysis showed the formation of substitutional solid solutions Cd_xPb_1–xSe with the NaCl structure, which contained 20, 40, 60, and 80 mol % cadmium selenide. The solid solutions were characterized by scanning electron microscopy, impedance spectroscopy, gas pycnometry, and Raman spectroscopy.     

Electrochemical synthesis,structure, and properties of nickel-tungsten-hydrogen ternary systems

The composition and structure of the electrochemically synthesized Ni-W-H alloys were studied. The co-deposition of nickel with tungsten mainly led to nickel solid solutions, and nanocrystalline alloys formed if the hydrogen content in them was at least 3 at %. The deposits included ∼2% of all evoluted hydrogen. The lattice constant of the solid solutions was 1.7–1.9% higher than the that of nickel. The tungsten solid solution phase found in a number of alloys was not nanocrystalline. The hardness of the alloys was several times higher than that of pure nickel.     

Phase equilibrium in the Pb2SnSb2S6-SnS system

The Pb₂SnSb₂S₆-SnS system was studied over a wide range of concentrations using a set of physicochemical methods (powder X-ray diffraction, DTA, microstructure examination, and microhardness measurement). A phase diagram for the title quasi-binary join was constructed for the first time. The phase diagram is of the eutectic type; the eutectic coordinates are 25 mol % SnS and 775 K. The extents of solid solutions based on the terminal components were determined to be 10 mol % SnS and 5 mol % Pb₂SnSb₂S₆. Alloys having compositions in the SnS-based solid solution region are semiconductors.     

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.     

Preparation and properties of new materials: Solid solutions (GaSb)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>(ZnTe)<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>

Solid substitutional solutions of cubic (sphalerite) lattice based on the binary semiconducting compounds GaSb and ZnTe in the range of their mutual solubility were synthesized. Their identification was performed on the basis of X-ray and electrophysical studies.     

Stabilized Zirconia-Based Nanostructured Powders for Solid-Oxide Fuel Cells

High-purity uniform powders of zirconia-based solid electrolytes stabilized with yttria (4 and 8 mol %) are synthesized by co-precipitation with subsequent annealing at different temperatures. The obtained powders were studied using X-ray analysis and transmission electron microscopy; the specific surface area was measured by nitrogen adsorption. The stabilized zirconia powder sintering was studied over temperature range from 1000 to 1600°C. The ionic conductivity of samples containing 8 mol % of yttria was 0.06–0.07 S/сm, that is comparable with that obtained with commercial solid electrolytes.     

Electrodeposition of Ni–Fe Alloys in the Presence of Complexing Agents

The electrodeposition of binary Ni–Fe alloys is studied in chloride-based solutions with organic additives. Specific codeposition composition of the electrolyte and operating variables are taken for deposition a wide range of Ni–Fe deposits. Results reveal that in solutions containing sodium citrate and glycolic acid, the nickel content always increases with the current density and nickel concentration. Therefore, nickel reduction rate and the Ni/Fe ratio in the deposits increase. The anomalous codeposition of iron is minimized and the quality of the alloy deposits is improved with the combination of sodium citrate and glycolic acid. Scanning electron micrographs show that, with addition of glycolic acid, the spherical particles become finer and the surface roughness relatively decreases. The XRD patterns of the Ni–Fe deposits exhibit the fcc structure and (111) preferred orientation for alloys with nickel content exceeding 60 wt %. After a heat treatment, additional peaks appear for an Ni–Fe solid solution.