


Том 55, № 10 (2019)
- Жылы: 2019
- Мақалалар: 16
- URL: https://journals.rcsi.science/0020-1685/issue/view/9635
Article
Electrical Properties of Electrochemically Grown Thin Sb2Se3 Semiconductor Films
Аннотация
Abstract—We have studied some of the electrical properties of thin Sb2Se3 semiconductor films produced by electrodeposition from tartrate electrolytes. The films have been shown to have n-type conductivity. In addition, we have determined some of their semiconductor constants: temperature sensitivity coefficient (B = 15 100 K), temperature coefficient of resistance (α = 0.167 K–1 at 300 K and 0.094 K–1 at 400 K), and band gap (Eg = 1.3 eV). The present results demonstrate that thin Sb2Se3 films can be used in solar cells and thermoelectric elements.



Growth of Arsenic-Doped Hg1– xCdxTe (x ~ 0.4) Epilayers by Metalorganic Chemical Vapor Deposition
Аннотация
We have studied arsenic incorporation from tris(dimethylamino)arsine into epitaxial Hg1– xCdxTe (x ~ 0.4) layers grown by the metalorganic chemical vapor deposition interdiffused multilayer process (MOCVD-IMP) on GaAs (310), (100), and (111)B substrates. CdTe was grown from dimethylcadmium and diethyltellurium vapors, and HgTe, from diisopropyltellurium and mercury vapors. Arsenic incorporation into the layers has been shown to depend on the crystallographic orientation of their growth, increasing in the order (111)B < (100) < (310). The addition of tris(dimethylamino)arsine during CdTe sublayer growth in an excess of diethyltellurium has been shown to have no significant effect on the macroscopic composition of the HgCdTe layers. The arsenic-doped HgCdTe layers have p-type conductivity. The fraction of electrically active arsenic in the layers depends on its concentration and rises from 15 to 85% in going from the (111)B to (100) and to (310) orientation. Additional two-step annealing ensures a near 100% arsenic activation in the HgCdTe layers.



Influence of Preloading and Deformation on the Grain Structure and Strength of the Ni3Al Intermetallic Compound Synthesized under Pressure
Аннотация
We have studied the influence of a preload applied to a starting elemental powder mixture and the strain in the product of high-temperature synthesis during a bulk exothermic reaction on the grain structure of the Ni3Al intermetallic compound and the temperature dependence of its strength. The results demonstrate that, during the bulk exothermic reaction responsible for the formation of the intermetallic compound under pressure in a closed press die, the average grain size varies along a vertical cut, from the minimum value on the upper and lower surfaces of the synthesized sample to the maximum value in its central part. As the preload applied to the starting powder mixture is raised, the average grain size decreases, whereas the general character of the grain size distribution in a cross section of the sample remains unchanged. Deformation of the high-temperature synthesis product in a press die with partial extrusion causes an appreciable grain size reduction, significantly averaging the grain size in the bulk of the synthesized sample, and raises the tensile strength of the intermetallic compound in the temperature range 20–1000°C.



Heterophase Synthesis of Zirconium Hydroxide from Zirconium Oxychloride
Аннотация
The effects of the nature and concentration of bases, as well as the reactants ratio and the process temperature on the properties of zirconium hydroxides synthesized via heterophase conversion of zirconium oxychloride have been studied. An optimal concentration range of the alkalis for the transformation of the precipitates from a gel-like state to a crystal-like one has been established. The transition process was found to be accompanied by a significant decrease of the apparent volume. The crystal-like zirconium hydroxide synthesized during the study inherited the morphological features of the initial zirconium oxychloride that can be considered as an anamorphosis phenomenon.



Crystal Structure of Solid Solutions in the Sm2O3–CaO–MO and Ln2O3–SrO–MO Systems (Ln = Sm, Gd; M = Fe, Co)
Аннотация
Complex oxides in the Sm2O3–CaO–MO and Ln2O3–SrO–MO systems (Ln = Sm, Gd; M = Fe, Co) were prepared via the glycerol-nitrate technique at 1100°С in air. The homogeneity ranges for the solid solutions were determined as follows: Sr1 – хGdхCoO3 – δ (0.1 ≤ х ≤ 0.4); Sr2 – yGdyCoO4 – δ (0.8 ≤ y ≤ 1.2); Sr1 – хGdхFeO3 – δ (0.05 ≤ х ≤ 0.30 and 0.80 ≤ х ≤ 1.0); Ca1 – xSmxFeO3 – δ (0.70 ≤ x ≤ 1.0); Sr2 – ySmyFeO4 – δ (0.7 ≤ y ≤ 0.8); Sr2 – yGdyFeO4 – δ (0.75 ≤ y ≤ 0.8); Ca2 – уSmуFeO4 – δ (у = 0.90); Sr3 – zSmzFe2O7 – δ (0 ≤ z ≤ 0.3 and z = 1.8); and Sr3 – zGdzFe2O7 – δ (0 ≤ z ≤ 0.3 and z = 1.9). For all single phase oxides, the crystal structure was determined and the unit cell parameters, the unit cell volume, and the structural parameters were refined.



Structural and Magnetic Properties of a BaFe12– xScxO19 Substituted Hexagonal Ferrite
Аннотация
Abstract—We have studied the effect of Sc3+ substitution for Fe3+ ions on the magnetic properties and crystal structure of BaFe12– xScxO19 hexaferrites. Based on Mössbauer spectroscopy data, we have assessed the distribution of scandium ions over sublattices and their effect on magnetic characteristics of the materials. The specific magnetization and coercive force of the ferrites have been shown to depend on the location and concentration of scandium ions in the crystal structure. The hexaferrite with x > 0.6 has been found to have a noncollinear magnetic structure.



Electrical Transport Properties of Ca1 –xBixMnO3 – δ
Аннотация
The electrical conductivity (σ) and thermoelectric power (S) of Ca1 –xBixMnO3 – δ (х = 0.05, 0.10, 0.15) manganites with a perovskite-like structure have been measured in air in the temperature range 298–1223 K. Doping with bismuth increases the electron charge carrier concentration and leads to an increase in σ and S. The observed decrease in σ and S with increasing temperature is due to partial Mn3+ disproportionation into Mn2+ and Mn4+.



Synthesis and Properties of (Ca/Sr)1 – 3xBi2xMoO4 Solid Solutions
Аннотация
We have synthesized CaMoO4- and SrMoO4-based scheelite-like compounds and located the stability ranges of (Ca/Sr)1 – 3xBi2xMoO4 solid solutions (x = 0.2125). The materials with x ≥ 0.175 have been shown to undergo superstructure ordering related to the arrangement of cation vacancies in their structure. The reflection spectra of the solid solutions have been measured and their band gap for direct transitions has been shown to range from 2.8 to 3.5 eV. We have studied photocatalytic properties of the solid solutions using powder samples. The photocatalytic characteristics of Ca1 – 3xBi2xMoO4 under UV illumination have been shown to be comparable to those of titania. The electrical conductivity of Ca1 – 3xBi2xMoO4 is lower than that of Sr1 – 3xBi2xMoO4.



Effect of Oxygen Pressure on the Thermodynamic Stability of Nd0.85Ba0.15MnO3
Аннотация
This paper presents a study of the structure of the Nd0.85Ba0.15MnO3 compound and its stability at a reduced oxygen partial pressure. Structural characteristics of Nd0.85Ba0.15MnO3 have been determined by X-ray diffraction. The sequence of phase transformations in the Nd–Ba–Mn–O system as the oxygen pressure decreases from atmospheric to –21 atm has been identified by a static method using a vacuum circulation apparatus.



Synthesis and Luminescence of Sr1– x – yYbxEuyF2+ x + y Solid Solutions for Photonics
Аннотация
Single-phase Sr1– x – yYbxEuyF2+ x + y solid solutions with an average particle size near 90 nm have been synthesized via co-precipitation from aqueous solutions, followed by high-temperature annealing. Efficient Yb3+ luminescence was observed upon excitation at a wavelength of 266 nm. The highest external quantum yield of ytterbium luminescence (2.5%) under pumping at a wavelength of 266 nm was reached for the SrF2:Yb(1.0 mol %),Eu(0.05 mol %) composition.



Crystallization Resistance of Optically Active GeSx〈Bi〉 Glasses
Аннотация
The crystallization kinetics of extrapure bismuth-doped Ge–S glasses, GeSx〈nBi〉 (1.25 ≤ х ≤ 1.6, n = 1 at %), have been studied by differential scanning calorimetry (DSC) in the range 320–1000 K. A technique proposed for analysis of crystallization peaks offers the possibility of describing them with an accuracy comparable to that of the Erofeev semiempirical model and includes analytical expressions for the degree of crystallization, α(t,Т), further developing a simplified version of the Kolmogorov–Johnson–Mehl theory. The kinetic characteristics of glass crystallization in α(t,Т) found using this technique and graphical representation of the data in the form of a time–temperature–transition (TTT) diagram make it possible to optimize the optical fiber drawing temperature and time.



Glass Transition of Liquids and Frozen Deformation of Glass
Аннотация
Abstract—We develop the notion that, near the glass transition temperature, amorphous substances undergo reversible configurational structural changes accompanied by local expansion and compression (atom delocalization). They are similar in nature to configurational changes in the structure of glasses in the case of reversible frozen deformation and its thermally stimulated relaxation.



Structure and Nanohardness of Compact Hydroxyapatite-Based Ceramics
Аннотация
Abstract—The substructure of hydroxyapatite ceramics produced by cold-pressing nanocrystalline hydroxyapatite powder, followed by annealing for 1–12 h at 1150°C, has been studied by transmission electron microscopy, and the hardness and modulus of elasticity of the ceramics have been determined using nanoindentation. The results demonstrate that the compaction process leads to coalescence of nanoparticles of the starting powder, which ensures a minimum hardness of the compact with a 50% relative density. The hardness and modulus of elasticity of HA ceramics increase with increasing firing time as a consequence of improvement of its substructure (an increase in grain size and a decrease in pore size and density).



Preparation and Properties of Copper-Substituted Hydroxyapatite Powders and Ceramics
Аннотация
Abstract—Hydroxyapatite powders containing up to 2.4 mol % Cu (Cu-HA) have been synthesized via precipitation from solution. The synthesized materials have been characterized by X-ray diffraction after heat treatment in the temperature range from 900 to 1400°C and their lattice parameters and crystallite size have been determined. We have studied the bending strength and microstructure of Cu-HA-based ceramics. The results demonstrate that the addition of more than 0.8 mol % copper reduces the thermal stability of HA, leading to its partial decomposition to monoclinic tricalcium phosphate (α-TCP) and its transformation into the hexagonal phase (β-TCP), with possible concentration of the copper in it. Increasing the percentage of copper leads to a decrease in HA sintering rate in combination with an increase in crystallite size and porosity. According to in vitro biological investigations, the ceramic materials are cytocompatible and their surface has marked matrix properties.



Synthesis, Properties, and Thermal Transformation of Organomagnesiumoxaneyttroxanealumoxanes
Аннотация
Abstract—This paper presents a study of organomagnesiumoxaneyttroxanealumoxane oligomers soluble in organic solvents and exhibiting fiber-forming properties. We describe processes underlying the formation of modified alumina structures as a result of the thermal transformation of organoelement precursors into ceramic phases. The physicochemical properties of the organomagnesiumoxaneyttroxanealumoxanes and ceramic samples prepared from them have been studied by nuclear magnetic resonance, IR spectroscopy, scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and elemental analysis. Polymer fibers have been produced by melt-spinning the fiber-forming organomagnesiumoxaneyttroxanealumoxanes.



Structuring Behavior of Composite Materials Based on Cement, Limestone, and Acidic Ash
Аннотация
Abstract—We have studied structure formation of cement stone with the use of silica-containing and inert additives and mechanochemical activation. Rational compositions and the particle size composition of composite binders have been determined by X-ray diffraction, differential thermal analysis, and microstructural analysis, which makes it possible to obtain preset physicomechanical characteristics of cement stone and related concrete. The synergistic effect of pozzolanic and inert additives has been shown to activate hydration processes, densifying the microstructure of newly formed phases.


