


Vol 54, No 8 (2018)
- Year: 2018
- Articles: 17
- URL: https://journals.rcsi.science/0020-1685/issue/view/9618
Article
Effect of Background Fe Impurities on the IR Absorption and Dielectric Response of High-Resistivity ZnSe Single Crystals
Abstract
High-resistivity zinc selenide crystals containing background impurities have been studied by IR spectroscopy and dielectric spectroscopy. Their IR absorption spectra contain a band attributable to the presence of background Fe impurities in the material. The dielectric characteristics of the ZnSe crystals lead us to conclude that, because of a nonuniform distribution of background impurities, they have the form of matrices containing inclusions.



Effect of Precursor Mixture Composition on the Phase Composition and Electrical Transport Properties of Cu1.85ZnSnS4 and Cu1.5Zn1.15Sn0.85S4 Kesterite Solid Solutions Prepared in Molten KI
Abstract
We have studied the effect of precursor mixture composition on the phase composition and electrical transport properties of Cu1.85ZnSnS4 and Cu1.5Zn1.15Sn0.85S4 solid solutions with the kesterite structure, prepared by reacting binary sulfides and sulfur in molten KI, and found conditions for the synthesis of Cu1.85ZnSnS4 and Cu1.5Zn1.15Sn0.85S4 solid solutions free from inclusions of impurity phases. The Cu1.5Zn1.15Sn0.85S4 and Cu1.85ZnSnS4 solid solutions have been shown to be p-type semiconductors.



Effect of Sn Doping on the Crystallization Kinetics of Amorphous TlInS2 Films
Abstract
The crystallization of amorphous Sn-doped TlInS2 films into three polymorphs has been studied by kinematic electron diffraction. The results demonstrate that the crystallization of 30-nm-thick amorphous films produced by thermal evaporation in high vacuum can be described by the Avrami–Kolmogorov equation: Vτ = V0[1–exp(–kτm)]. Kinematic electron diffraction patterns of the TlIn1–хSnxS2 films have been used to assess the effect of doping with Sn on the growth dimensionality and the activation energy for the crystallization of the amorphous films and the unit-cell parameters of the resultant crystalline materials. Doping extends the temperature range and effective activation energy for the crystallization of the amorphous films.



Synthesis of Porous Composite Materials via Combustion of a Mixture of Titanium, VT6 Alloy, and Amorphous Boron Powders
Abstract
Self-propagating high-temperature synthesis without preheating has been realized in powder mixtures consisting of large spherical VT6 titanium alloy granules, small dendritic titanium particles, and black amorphous boron. Synthesis in a combustion wave involved a few steps: first, boron reacted with fine-particle titanium to form a boride matrix, which then reacted with molten VT6 titanium alloy granules. We have obtained a porous metal–ceramic material similar in structure to composites.



Silicidation of Tantalum Carbide and Zirconium Carbide Powders in a Gaseous SiO Environment
Abstract
Tantalum carbide and zirconium carbide powders have been silicided in a gaseous SiO atmosphere at 1400°C. X-ray diffraction and energy dispersive X-ray microanalysis results demonstrate that the silicidation products are Ta5Si3 and TaSi2 in the case of TaC and ZrSi in the case of ZrC. The silicidation rate has been shown to influence the percentages of these silicides in the reaction products. The degree of silicidation reached in this study is about 20% in the case of TaC and about 16% in the case of ZrC.



Preparation of a SiC Fiber Textile Material
Abstract
A textile material consisting of SiC fibers has been produced by siliciding carbon cloth in a gaseous SiO atmosphere. The reactive SiO source used was a mechanical mixture of silicon and silicon dioxide. The process was run at a temperature of 1400°C under dynamic vacuum. The results demonstrate the conceptual feasibility of using the process for producing SiC cloth reproducing the dimensions and shape of the parent carbon cloth.



Electrical Conductivity and Electrochemical Characteristics of Na3V2(PO4)3-Based NASICON-Type Materials
Abstract
NASICON-type materials with the compositions Na3V2–xAlx(PO4)3, Na3V2 - xFex(PO4)3, Na3 + xV2–xNix(PO4)3, and Na3V2 - xCrx(PO4)3 (x = 0, 0.03, 0.05, and 0.1) have been prepared and characterized by X-ray diffraction analysis, electron microscopy, and impedance spectroscopy. The results demonstrate that the highest electrical conductivity among the samples studied is offered by the material doped with 5% Fe: Na3V1.9Fe0.1(PO4)3. The activation energy for low-temperature conduction in the doped materials decreases from 84 ± 2 to 54 ± 1 kJ/mol and that for high-temperature conduction is ~33 kJ/mol. The discharge capacity of Na3V1.9Fe0.1(PO4)3/C under typical working conditions of cathodes of sodium ion batteries has been shown to exceed that of Na3V2(PO4)3/C. The capacity of the more porous material prepared by the Pechini process (Na3V1.9Fe0.1(PO4)3/C-{II}) approaches the theoretical one at a low charge–discharge rate and retains its high level as the charge rate is raised (its discharge capacity was 117.6, 108.8, and 82.6 mAh/g at a discharge rate of 0.1C, 2C, and 8C, respectively).



Quartz Concentrates Based on Compact Quartzite
Abstract
This paper presents a study of a variety of quartz material from East Sayan: compact quartzite from the Oka–Urik block. We have investigated the texture and structure of quartz and mineral and fluid inclusions in it. It has been shown that the fluid inclusions are located mainly in the quartz grains and that the major salt component in the fluid inclusions is sodium. In the case of compact quartz, we have proposed a process for the preparation of extrapure quartz concentrates. A distinctive feature of the process is high-temperature precalcination of quartz grit prior to chemical enrichment, which makes it possible to open the fluid inclusions and remove sodium.



Activating Effect of Aluminum Chloride in the Preparation of Sulfur Concrete from Sulfur and Silica
Abstract
Using physicochemical characterization techniques and quantum-chemical calculations, we have demonstrated that aluminum chloride has an activating effect on the chemical interaction between sulfur and silica. As a result, we have developed a low-waste process for producing sulfur concrete with good physicomechanical and functional properties.



Synthesis and High-Temperature Heat Capacity of Neodymium Titanate
Abstract
Neodymium dititanate, Nd2Ti2O7 (monoclinic structure, sp. gr. P21), has been prepared by solid-state reaction in air at temperatures from 1673 to 1773 K using the Nd2O3 and TiO2 oxides as starting materials. The high-temperature heat capacity of the resultant polycrystalline Nd2Ti2O7 samples has been determined by differential scanning calorimetry. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of neodymium dititanate (enthalpy increment H°(T)–H°(320 K), entropy change S°(T)–S°(320 K), and reduced Gibbs energy Ф°(T)) in the temperature range 320–1053 K.



Mechanochemical Synthesis of Sr-Substituted Hydroxyapatite
Abstract
We demonstrate that a nanoparticulate Sr-substituted carbonate hydroxyapatite can be prepared by fast mechanochemical synthesis, without further annealing of the material. The synthesis process takes 30 min and yields single-phase products. We have obtained a series of Ca10–xSrx(PO4)6(OH)2 samples with x = 0–2.



Flux Growth, Thermal Properties, and Luminescence Spectra of (Er,Yb,Lu)Al3(BO3)4 Solid Solutions
Abstract
We have studied phase relations in the pseudoquaternary system LuAl3(BO3)4–(K2Mo3O10–Al2O3–B2O3) in the temperature range 1130 to 900°C. The phase relations were represented in graphical form, as a projection of the formation of solid phases in this range onto the composition triangle at 900°C. Optimal results in terms of high-temperature solution growth have been obtained at 25 wt % LuAl3(BO3)4 in the growth charge. Undoped and erbium–ytterbium codoped LuAl3(BO3)4 (LuAB) single crystals have been grown from high-temperature solutions on “pointlike” seeds. The (Er,Yb):LuAB crystals are similar in thermal properties and luminescence spectra to (Er,Yb):YAl3(BO3)4 and (Er,Yb):GdAl3(BO3)4 crystals and can be used in diode-pumped lasers operating in the nominally eye-safe spectral region 1.5–1.6 μm.



Sol–Gel Synthesis and Distinctive Structural Features of CexZr1–xO2 Solid Solutions
Abstract
We have synthesized CexZr1–xO2 solid solutions via the thermal decomposition of xerogels of different compositions prepared by drying appropriate hydrosols. The synthesized materials have been characterized by thermal analysis, X-ray diffraction, and Raman spectroscopy. The results demonstrate that the solid solutions are formed at relatively low temperatures (450–600°C). The CexZr1–xO2 samples with x = 0.5–0.9 consist of a cubic solid solution. At a lower CeO2 content (x = 0.2), the material consists of a mixture of cubic and tetragonal phases.



Liquid–Vapor Equilibria in the SiCl4–A (A = SiCl4–nFn (n = 1–4) Impurity) Systems
Abstract
The vapor–liquid separation factors of SiCl4–A (A = SiCl4–nFn (n = 1–4) silicon fluorochloride impurities in silicon tetrachloride have been determined experimentally at 298 K by statically balancing phases. The values obtained for the SiCl4–SiCl3F, SiCl4–SiCl2F2, SiCl4–SiClF3, and SiCl4–SiF4 systems are 4.9 ± 0.8, 8.2 ± 1.2, 29.8 ± 6.1, and 42.0 ± 7.5, respectively. In the SiCl4–SiCl3F system, the vapor–liquid separation factor has also been determined by the Rayleigh distillation method: α = 5.0. The experimental data agree with the vapor–liquid separation factors estimated in conformal solution theory using parameters of the Lennard- Jones potential.



Effects of Mechanical Load and Ionizing Radiation on Glass
Abstract
This paper develops an approach to investigation of a solid as an integral system whose fundamental properties are determined by the energetics of its structure. Addressing the subject from a unified viewpoint, we consider the formation, accumulation, and transformations of defects in silicate and aluminophosphate glasses, which emit electromagnetic waves in a wide frequency range as a result of cracking. It has been shown that electron irradiation causes spontaneous electrical discharges, whose magnitude depends on the electron energy and irradiation time. The discharges occur at surface defects. Brush discharges develop in a layer where charged particles are distributed. In a thin layer of a charged dielectric, we observe a breakdown effect. The electrical discharge concentrates at surface defects, which can be produced in advance. A discharge can be initiated by approaching a grounded metallic tip to a charged surface even some time after irradiation. A discharge, mechanical loading, cooling, or heating of glass is accompanied by not only a light burst but also electromagnetic emission (EME), which correlates well with a polymorphic transformation process, thermoluminescence, etc. Thus, the release of accumulated energy from unirradiated and irradiated inorganic glasses on heating and cooling is accompanied by pulsed EME, whose intensity depends on the energy stored in the material.



Influence of the Preparation Conditions and Percolation Threshold on the Properties of Lead Zirconate Titanate/Cobalt Nickel Ferrite Magnetoelectric Composites
Abstract
We have prepared magnetoelectric (ME) composite ceramics, free of foreign phases, in the lead zirconate titanate–cobalt nickel ferrite two-phase system: xPZT-36 + (100–x)Ni0.9Co0.1Fe2O4. The sol–gel derived ferrite powder used in our preparations seems to be doped with titanium cations from the PZT-36. The ceramics have a percolation threshold at x = 50–70 wt %, which is due to the increased electrical conductivity of Ni0.9Co0.1Fe2O4. As a consequence, the piezoelectric parameters of the ME ceramics drop sharply at x < 50–70 wt %: the piezoelectric moduli |dij| and piezoelectric voltage coefficients |gij| decrease by a factor of 3–5 in this composite range. The piezoelectric parameters |dij| and |gij| of the composites produced using the fine ferrite powder exceed those of the materials prepared using macrocrystalline Ni0.9Co0.1Fe2O4 powder by more than a factor of 2. The piezoelectric voltage coefficient g33 correlates with the ME coefficient ΔE/ΔH. The highest ME conversion efficiency (up to 45 mV/(cm Oe)) is offered by the 80 wt % PZT-36 + 20 wt % Ni0.9Co0.1Fe2O4 composites, whose composition lies in a subpercolation region. Even though the composites produced using the fine ferrite powder possess improved piezoelectric properties, they have smaller ΔE/ΔH coefficients (no greater than 25 mV/(cm Oe)), which can be tentatively attributed to the degradation of the properties of the ferrite as a consequence of doping with Ti4+ cations during the sintering of the composite ceramics.



Physicochemical Modeling and Modification of the Composition of Magmatic and Metamorphic Rocks: Diorites
Abstract
This paper presents general data on the diorite family: intermediate plutonic rocks in the normally and low alkaline rock subclass. Using quartz diorite from the Altai Mountains as an example, we analyze the feasibility of using methods developed at the Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, for modifying the composition of magmatic and metamorphic rocks for mineral fiber fabrication and stone casting.


