Inorganic Materials (v.52, #11)
Amorphous silica containers for germanium ultrapurification by zone refining by O. I. Podkopaev; A. F. Shimanskii; T. V. Kulakovskaya; A. N. Gorodishcheva; N. O. Golubovskaya (1091-1095).
We have studied the wetting behavior of molten germanium on silica ceramics and amorphous silica coatings in vacuum at a pressure of 1 Pa and a temperature of 1273 K. The results demonstrate that the wetting of rough surfaces of ceramic samples and coatings by liquid Ge is significantly poorer than that of the smooth surface of quartz glass. The contact angle of polished glass is ~100°, and that of the ceramics and coatings increases from 112° to 137° as the total impurity content of the material decreases from 0.120 to 1 × 10–3 wt %. Using experimental contact angle data, we calculated the work of adhesion of molten Ge to the materials studied. Its value for the surface of the ceramics and coatings decreases from 0.45 to 0.20 J/m2 with decreasing impurity content, whereas the work of adhesion to a smooth glass surface is 0.55 J/m2. We have fabricated fused silica test containers coated with high-purity amorphous silica. Using horizontal zone refining, we obtained germanium samples with a carrier concentration difference on the order of 1011 cm–3.
Keywords: melt; container materials; amorphous silica; fused silica; ceramic; contact angle; work of adhesion
Complex dielectric permittivity and electrical conductivity of (TlGaSe2)1–х (TlInS2) х solid solutions in an AC electric field by S. N. Mustafaeva; S. M. Asadov; M. M. Gojaev; A. B. Magerramov (1096-1102).
We have synthesized the TlGaSe2 and TlInS2 compounds and (TlGaSe2)1–х (TlInS2) х (х = 0.2, 0.4) solid solutions. The phase composition of the (TlGaSe2)1–х (TlInS2) х (х = 0, 0.2, 0.4, 1.0) samples and crystals grown using these materials has been determined by X-ray diffraction. TlGaSe2, TlInS2, and the TlGaSe2-based solid solutions (monoclinic crystal system) have been shown to be isostructural with each other. The dielectric properties of the grown crystals have been studied in ac electric fields at frequencies in the range f = 5 × 104 to 3.5 × 107 Hz. We have identified the relaxation nature of the dielectric permittivity of the crystals, the origin of the dielectric loss, and the hopping carrier transport mechanism in the samples. It has been shown that, with increasing x, the mean hop distance and time in the (TlGaSe2)1–х (TlInS2) х solid solutions decrease, whereas the concentration of deep traps and the energy spread of the states localized in the band gap increase.
Keywords: (TlGaSe2)1–х (TlInS2)х solid solutions; dielectric permittivity; hopping conduction; frequency dispersion; dielectric loss
Electrochemical synthesis, cathodoluminescence, and optical absorption of CdS and Cd1–х Zn х S (0 < x ≤ 0.017) films by E. A. Senokosov; I. N. Odin; M. V. Chukichev; V. M. Ishimov; I. V. Demidenko; R. R. Rezvanov (1103-1107).
Using electrochemical deposition from an aqueous solution of Na2S2O3 and CdSO4, with a cadmium anode, we have grown CdS films on tin dioxide substrates (cathode). The CdS films have been shown to be polycrystalline, with the wurtzite structure. From the optical absorption and cathodoluminescence spectra of the films, we have determined their band gap at 298 and 78 K. With a zinc anode, we obtained polycrystalline Cd1–х Zn х S (0 < x ≤ 0.017) films with the wurtzite structure. The Cd0.983Zn0.017S films have a larger band gap and higher luminescence intensity than do the CdS films.
Keywords: electrochemical synthesis; films; lattice parameters; optical absorption; cathodoluminescence; band gap
Distribution of luminescence centers in the bulk of undoped, Fe-doped, and Cr-doped CVD ZnSe polycrystals studied by two-photon confocal microscopy by E. M. Gavrishchuk; A. A. Gladilin; V. P. Danilov; V. B. Ikonnikov; N. N. Il’ichev; V. P. Kalinushkin; A. V. Ryabova; M. I. Studenikin; N. A. Timofeeva; O. V. Uvarov; V. A. Chapnin (1108-1114).
Edge and defective-impurity luminescence in polycrystalline CVD ZnSe has been studied in the range 0.46–0.73 μm by two-photon confocal microscopy. We have obtained luminescence intensity distribution maps for undoped, iron-doped, and chromium-doped ZnSe samples at depths of up to 1 mm with a spatial resolution of a few microns. It has been shown that crystal regions with low dopant concentrations contain centers that luminesce in the ranges 520–580 and >670 nm. The parts of the crystals with high iron and chromium concentrations contain centers that suppress the edge and defective-impurity (520–580 nm) luminescence. We discuss the nature of these centers and demonstrate the possibility of assessing the luminescence characteristics of grain boundaries in CVD ZnSe.
Keywords: Fe2+:ZnSe; Cr2+:ZnSe; thin films; photoluminescence spectra; confocal microscopy
Effect of magnesium on the performance characteristics of ZnS:Cu,Mn phosphors by K. A. Ogurtsov; M. M. Sychov; V. V. Bakhmetyev; V. N. Korobko; A. I. Ponyaev; F. I. Vysikailo; V. V. Belyaev (1115-1120).
We have studied the effect of magnesium added to the starting mixture as MgS or MgCl2 on the performance characteristics of synthesized ZnS:Cu,Mn phosphor powders. It has been shown that the incorporation of certain amounts of magnesium into the ZnS:Cu,Mn phosphor leads to an increase in photo- and electroluminescence brightness and is favorable for Mn incorporation into the structure of the phosphor. In particular, additional doping of a dc electroluminescent ZnS:Cu,Mn phosphor with 30 mol % Mg ensured not only a shift of its luminescence spectrum to shorter wavelengths, thereby extending the color range of light sources, but also a twofold increase in its brightness.
Keywords: phosphor; brightness; emission; manganese; doping
Heat treatment-induced phase transformations of materials in a system of calcium phosphates and magnesium phosphates with (Ca + Mg)/P = 2 by M. A. Goldberg; V. V. Smirnov; O. S. Antonova; L. I. Shvorneva; S. V. Smirnov; S. V. Kutsev; S. M. Barinov (1121-1125).
We have studied the effect of heat treatment in a wide temperature range (from 300 to 1500°C) on the phase composition, heat effects and weight loss of powder materials in a system of calcium phosphates and magnesium phosphates with (Ca + Mg)/P = 2. The results demonstrate that crystalline magnesium-substituted whitlockite phases begin to form at temperatures above 600°C. Raising the heat treatment temperature reduces the degree of magnesium substitution for calcium in the structure of the magnesium-substituted whitlockite. Tetracalcium phosphate, a high-temperature phase, is formed through apatite phase recrystallization.
Keywords: magnesium-substituted whitlockite; apatite phase; degree of substitution
Hydriding of TiMo alloys at high hydrogen pressures by S. A. Lushnikov; E. A. Movlaev; I. A. Bobrikov; V. G. Simkin; V. N. Verbetsky (1126-1131).
We studied the interaction of Ti0.40Mo0.60 and Ti0.34Mo0.66 alloys with hydrogen and obtained hydrogen desorption isotherms at pressures of up to 250 MPa. At high hydrogen pressures, we observed the formation of Ti0.40Mo0.60Н1.1 and Ti0.34Mo0.66Н0.8 hydride phases. According to X-ray diffraction data, the hydrides consisted of phases with a body-centered cubic and face-centered cubic (CaF2 structure) lattices. The structure of the deuteride based on the Ti0.40Mo0.60 alloy was studied by neutron diffraction. We identified the sites occupied by deuterium atoms and determined their occupancies.
Keywords: hydrides; desorption isotherms; neutron diffraction
Mo/Ni and Ni/Ta–W–N/Ni thin-film contact layers for (Bi,Sb)2Te3-based intermediate-temperature thermoelectric elements by D. G. Gromov; Yu. I. Shtern; M. S. Rogachev; A. S. Shulyat’ev; E. P. Kirilenko; M. Yu. Shtern; V. A. Fedorov; M. S. Mikhailova (1132-1136).
We have examined the possibility of utilizing thin-film contact layers for producing reliable Ohmic contacts to proposed intermediate-temperature (Bi,Sb)2Te3-based thermoelectric materials with improved thermoelectric properties, which allow the working temperature range to be extended to 600 K. Three contact configurations have been produced by ion-plasma magnetron sputtering: a single Ni layer, Mo/Ni bilayer, and Ni/Ta–W–N/Ni three-layer system. It has been shown that reliable contacts can be produced using Mo/Ni and Ni/Ta–W–N/Ni layers, which prevent interdiffusion between the materials to be joined and ensure good adhesion to the thermoelectric element.
Keywords: thermoelectric materials; thin films; thermoelectric element; diffusion barrier; adhesion; Auger electron spectroscopy
Effect of particle size on the conductive and electrochemical properties of Li2ZnTi3O8 by P. A. Nikiforova; I. A. Stenina; T. L. Kulova; A. M. Skundin; A. B. Yaroslavtsev (1137-1142).
We have studied the effect of final annealing temperature on the formation of lithium zinc titanate, its electrical conductivity, and its electrochemical performance. Li2ZnTi3O8 has been shown to form in a wide range of annealing temperatures, from 673 to 1073 K. Its particle size increases systematically with increasing annealing temperature, whereas its conductivity decreases. The highest electrochemical capacity at low currents is offered by the materials annealed at 773 and 873 K, and the highest cycling stability is offered by the material prepared at 873 K.
Keywords: lithium zinc titanate; Li2ZnTi3O8 ; lithium ion battery; anode material; ionic conductivity
Effect of the chemical nature of precipitants on the formation of ultrafine YAl3(BO3)4:Ce powders by Yu. V. Bokshits; N. Yu. Brezhneva; G. P. Shevchenko (1143-1148).
Ultrafine Ce3+-doped YAl3(BO3)4 powders have been synthesized through coprecipitation using ammonia, ammonium bicarbonate, and ammonium oxalate as precipitants. We have studied the effect of the nature of the precipitants on the formation of YAl3(BO3)4:Ce and its structural properties, morphology, and luminescence spectrum.
Keywords: yttrium aluminum borate; precipitation; precursor; ultrafine powders
Low-temperature heat capacity of yttrium orthotantalate by M. A. Ryumin; E. G. Sazonov; V. N. Guskov; G. E. Nikiforova; P. G. Gagarin; A. V. Guskov; K. S. Gavrichev; L. Kh. Baldaev; I. V. Mazilin; L. N. Golushina (1149-1154).
The heat capacity of yttrium orthotantalate has been determined as a function of temperature by adiabatic calorimetry in the temperature range 0–340 K. Smoothed heat capacity data have been used to calculate the thermodynamic functions of yttrium orthotantalate.
Keywords: adiabatic calorimetry; thermodynamic functions
Effect of synthesis conditions on the particle size and luminescence properties of the La3.16Gd10Yb0.7Er0.14Ge2B6O34 germanate borate by V. A. Krut’ko; M. G. Komova; D. V. Pominova; A. B. Yaroslavtsev (1155-1159).
La3.16Gd10Yb0.7Er0.14Ge2B6O34 germanate borates have been synthesized using liquid-phase homogenization of starting materials. The smallest crystallite size, 25.3 ± 0.8 nm, has been obtained using a combination of two complexing agents (citric acid and mannitol). We have determined the energy yield of upconversion luminescence in the synthesized borates. Using tartaric acid as a complexing agent, we have obtained a phosphor with an energy yield of upconversion luminescence B en = 0.52% (λex = 974 nm, P = 2.5 W/cm2) and crystallite size of 80.6 ± 0.5 nm.
Keywords: synthesis of germanate borates; upconversion nanophosphors
Surface modification of elongated one-dimensional titanium dioxide structures with ferromagnetic nanoparticles by T. M. Zima; I. Yu. Prosanov (1160-1165).
Nanostructured TiO2 in the form of elongated one-dimensional structures having a highly ordered layered morphology, with cobalt-containing agglomerates on their surface, has been prepared by hydrothermal treatment of CoTiO3 powder in the presence of chitosan, a bioactive natural polymer. The synthesis products have been characterized by scanning electron microscopy, transmission electron microscopy, IR spectroscopy, X-ray diffraction, elemental analysis, and magnetic measurements. The structures have been shown to be up to several microns in length, and their typical width ranges from 100 to 400 nm. The one-dimensional structures retain high thermal stability at calcination temperatures of up to 800°C. After vacuum heat treatment at 600°C and above, the nanostructured material possesses anomalously high ferromagnetic characteristics.
Keywords: nanostructured TiO2 ; hydrothermal treatment; one-dimensional structures; ferromagnetic properties
Structure and microwave dielectric properties of ZnTa2O6 ceramics with TiO2 and ZrO2 additions by S. S. Redozubov; N. F. Kartenko; I. M. Gaidamaka; E. A. Nenasheva (1166-1171).
Ceramic samples based on ZnTa2O6 and ZnTa2O6–MO2 (M = Ti, Zr) systems have been obtained by the solid state ceramic route. The phase composition and microstructure of samples were investigated. The effect of the aliovalent substitution of ions Zn2+ and Ta5+ by M4+ (M = Ti, Zr) in the structure of ZnTa2O6 on microwave dielectric properties of ceramics was studied. The way of the compensation of the positive temperature coefficient of resonant frequency of dielectric resonators based on ZnTa2O6 ceramics with using the aliovalent substitution of cations was proposed. Dielectric resonators with the high temperature stability of the resonant frequency and high dielectric properties in the microwave range based on the ZnTa2O6–ZrO2 system were obtained for application in electronics.
Keywords: aliovalent substitution; crystal structure; dielectric resonators
Low-firing binders from magnesium containing carbonate raw materials by N. S. Shelikhov; R. Z. Rakhimov; R. R. Sagdiev (1172-1178).
This paper presents scientific and experimental data for low-firing hydraulic binders: hydraulic lime and Roman cement based on local mineral raw materials. The binders were prepared by firing representative samples of carbonate–clay magnesian raw materials from Tatarstan. Using X-ray diffraction, we identified the firing products, including a hydraulically active phase, and determined the structural characteristics of its minerals. The compositions of the binders were determined as functions of firing conditions. We examined the influence of the firing temperature and duration of magnesian raw materials in the preparation of binders on MgO activity and demonstrated for the first time the possibility of ensuring an active state of the MgO resulting from firing (up to 21%) and suppressing its negative effect on Roman cement and hydraulic lime hardening processes.
Keywords: hydraulic lime; Roman cement; raw materials; firing; active magnesium oxide
Gadolinium and lutetium hafnates: Materials for the preparation of high-quality optical coatings by B. M. Zhigarnovskii; V. A. Samokhov; A. V. Kopytin; A. G. Beirakhov; V. V. Kirilenko; E. G. Il’in; A. V. Mikhailov (1179-1182).
We have studied the spectroscopic properties and service performance of gadolinium hafnate and lutetium hafnate optical coatings. The coatings have been shown to possess improved optical parameters in comparison with binary oxide films and enhanced optical damage threshold
Keywords: gadolinium and lutetium hafnates; film-forming materials; optical coatings
Modeling of the evaporation of liquids and condensation of their vapor during distillation by Yu. P. Kirillov; V. A. Shaposhnikov; L. A. Kuznetsov; V. S. Shiryaev; M. F. Churbanov (1183-1188).
This paper considers the evaporation process in an evaporator–connecting tube–condenser system under conditions such that the evaporation rate is determined by the evaporation and condensation mechanisms and the hydraulic resistances of the evaporation and condensation compartments and connecting tube. We present a mathematical model and numerical simulation results that demonstrate quantitative patterns of a steady-state evaporation process in a closed evaporation–condensation system. For a particular example of selenium vacuum distillation, we have determined the evaporation coefficient of selenium from experimental data on the temperature dependences of the selenium evaporation rate and saturated vapor pressure.
Keywords: evaporation; condensation; mass transport; closed system; evaporation coefficient; selenium
Mechanochemical synthesis of fine-particle γ-LiAlO2 by V. P. Isupov; Ya. E. Trukhina; N. V. Eremina; N. V. Bulina; I. A. Borodulina (1189-1197).
Using thermogravimetry, in situ X-ray diffraction, room-temperature X-ray diffraction, specific surface area measurements, and particle size analysis, we have studied how preliminary mechanical activation of a mixture of aluminum hydroxide and lithium carbonate in an AGO-2 planetary mill and subsequent heat treatment of the mixture influence the synthesis of fine-particle nanostructured gamma-lithium monoaluminate. We have proposed a scheme of the structural changes accompanying the synthesis of gamma-lithium monoaluminate.
Keywords: mechanical activation; aluminum hydroxide; lithium carbonate; heat treatment; gamma-lithium monoaluminate
Dielectric properties of composite materials containing aligned carbon nanotubes by O. S. Yakovenko; L. Yu. Matzui; L. L. Vovchenko; V. V. Oliynyk; V. L. Launetz; A. V. Trukhanov (1198-1203).
This paper presents a study of the electrodynamic properties of polymer-matrix composite materials containing a filler in the form of multiwalled carbon nanotubes. We have examined the effect of filler alignment in the composites on their interaction with electromagnetic radiation. The composite materials have an anisotropic electrical conductivity, dielectric permittivity, and electromagnetic radiation attenuation coefficient because an applied electric field produces a preferential filler alignment direction.
Keywords: carbon nanotubes; composite materials; dielectric permittivity; electromagnetic shielding; anisotropy