Inorganic Materials (v.47, #3)

Effect of emitter current on the properties of the collector junction in silicon and germanium transistor structures by E. A. Jafarova; Z. A. Iskenderzade; L. A. Alieva; E. S. Taptygov (213-217).
We have studied the effect of emitter current on the capacitance of a forward-biased collector junction in silicon and germanium transistor structures. The results demonstrate that nonequilibrium carriers in the collector junction at a nonzero emitter current are responsible for an additional capacitance and facilitate conversion of the net capacitance of the collector junction to an inductance (negative capacitance). Therefore, both the magnitude and sign of the collector capacitance can be controlled by varying the emitter current. Experimental evidence is presented that, at high emitter currents, the barrier capacitance of the collector junction in the transistor structures may both increase and decrease, depending on the nature of the junction and the doping levels in the base and collector regions. Our experimental data agree well with calculation results.

Effect of the oxidation state of the praseodymium ion on the optical properties of PrSb2 films by Z. U. Jabua; A. V. Gigineishvili; I. G. Tabatadze (218-222).
A process has been developed for the growth of thin crystalline PrSb2 films by thermal evaporation using Pr and Sb separate sources. The room-temperature optical spectra (reflectivity, absorption coefficient, loss function, real and imaginary parts of dielectric permittivity) of PrSb2 films containing praseodymium in different oxidation states have been studied at photon energies from 0.05 to 5.5 eV. The behavior and energy position of features in the spectra have been analyzed. Independent of the oxidation state of the praseodymium ion, there is a gap in the energy spectrum and a sharp plasma edge in the reflection spectrum. Reducing the oxidation state of Pr decreases the plasma frequency and the effective number of carriers that contribute to plasma oscillations.

Fluorescent CdS nanoparticles for cell imaging by S. V. Rempel; N. S. Kozhevnikova; N. N. Aleksandrova; A. A. Rempel (223-226).
Fluorescent cadmium sulfide nanoparticles stabilized by an organic shell based on ethylenediaminetetraacetic acid have been prepared by chemical condensation in an aqueous solution. The nanoparticle concentration in aqueous solutions has been optimized and it has been shown that such hybrid nanoparticles can be used to image cell cultures and explore the cell structure. Not only the nanoparticle concentration but also the incubation time of the nanoparticle solution with the cell culture are essential for observing structural details.

Thermodynamic properties of arsenic sulfides studied by EMF measurements by M. B. Babanly; G. V. Muradova; T. M. Il’yasly; D. M. Babanly (227-230).
The solid-state phase equilibria and thermodynamic properties of alloys in the As-S system have been studied using emf measurements. The temperature and composition dependences of the emf confirm the existence of As2S5, As2S3, AsS, and As4S3 with narrow homogeneity ranges. The emf data are used to calculate relative partial molar functions of the As in the alloys and the standard Gibbs energies and standard entropies of the arsenic sulfides.

Phase relations in the CuAsS2-MS (M — Pb, Eu, Yb) systems by S. T. Bairamova; M. R. Bagieva; S. M. Agapashaeva; O. M. Aliev (231-234).
The CuAsS2-PbS, CuAsS2-EuS, and CuAsS2-YbS systems have been studied for the first time and their phase diagrams have been mapped out. We have identified the MCuAsS3 (M — Pb, Eu, Yb) compounds (seligmannite structure, Z = 4, sp. gr. Pmn21) and determined their lattice parameters: a = 8.125, b = 8.748, c = 7.644 Å (PbCuAsS3); a = 8.04, b = 8.66, c = 7.60 Å (EuCuAsS3); a = 8.00, b = 8.62, c = 7.54 Å (YbCuAsS3).

Homogeneity ranges and thermodynamic properties of ternary phases in the SnTe-Bi2Te3-Te system by M. B. Babanly; F. N. Guseinov; G. B. Dashdyeva; Yu. A. Yusibov (235-239).
The Sn-Bi-Te system has been studied in the composition region SnTe-Bi2Te3-Te at temperatures from 300 to 430 K using emf measurements on reversible concentration cells of the type $$ ( - )SnTe(s)|liquid electrolyte, Sn^{2 + } |(Sn - Bi - Te)(s)( + ) $$ The subsolidus phase diagram inferred from the emf data includes the ternary compounds SnBi2Te4, SnBi4Te7, and SnBi6Te10 and a broad (0–25 mol % SnTe) range of Bi2Te3-based solid solutions. Best fit equations for the temperature-dependent emf data were used to determine the differences between the partial thermodynamic functions ( $$ overline {Delta G} ,overline {Delta H} $$ and $$ overline {Delta S} $$ ) of the Sn in SnTe and SnTe-Bi2Te3-Te alloys. From these partial molar functions, we calculated the standard thermodynamic functions of formation and standard entropies of the β-solution and ternary compounds by integrating the Gibbs-Duhem equation along the SnTe-Bi2Te3 join with the use of the relevant data for SnTe and Bi2Te3.

NdRh3-based intermetallic hydrides by S. A. Lushnikov; S. N. Klyamkin; T. V. Filippova; K. M. Podurets; A. V. Gribanov (240-244).
We have studied chemical interaction of the intermetallic compound NdRh3 with hydrogen at pressures of up to 0.2 GPa. The structural changes in the intermetallic matrix in different stages of the hydrogenation process have been followed using synchrotron X-ray diffraction. The results demonstrate that hydrogen absorption leads to an irreversible change in lattice symmetry from hexagonal to cubic.

Crystal Structure of TbNiD3.3 by Yu. L. Yaropolov; S. S. Agafonov; V. P. Glazkov; V. A. Somenkov; V. N. Verbetsky (245-250).
A TbNi-based deuteride has been prepared by hydriding TbNi at a temperature of 297 K and a deuterium pressure no higher than 0.25 MPa. The structure of TbNiD3.3 differs from that of the parent intermetallic compound, indicating that deuteration causes structural changes in the metallic sublattice. The deuteride has an orthorhombic structure (CrB type, sp. gr. Cmcm) in which the deuterium atoms occupy three positions, 4c, 8f, and 4b, with [Tb3Ni2], [Tb3Ni], and [Tb4Ni2] nearest neighbor environments, respectively.

Structure of multiwalled carbon nanotubes grown by chemical vapor deposition by E. M. Baitinger; N. A. Vekesser; I. N. Kovalev; A. A. Sinitsyn; I. A. Tsygankov; Yu. I. Ryabkov; V. V. Viktorov (251-254).
Carbon nanotubes have been grown by chemical vapor deposition at 650°C in an argon atmosphere using a butane-propane mixture and a nickel catalyst and have been characterized by scanning and transmission electron microscopy and Raman spectroscopy. The results indicate that the multiwalled nanotubes have an imperfect graphite-like structure with a conical supramolecular configuration. A phenomenological technique is proposed for statistical analysis of the state of carbon nanotubes in measurements of the intensity of the defect zone D in their Raman spectra.

Diamond films were deposited on molybdenum substrates from mixtures of methane diluted in hydrogen using a high-pressure microwave plasma reactor. In this reactor, a compressed waveguide structure was used to increase the electric field strength, and accordingly the reactor was able to operate stably with low gas flow rate and microwave power. The films deposited on 12 mm diameter substrates were characterized by film morphology, Raman spectra, growth rate and crystalline quality. The morphology of diamond films deposited in this reactor depends mainly on the substrate temperature. When the deposition pressure was 48 kPa and microwave power was only 800 W, high quality diamond films could be uniformly deposited with a growth rate around 20 μm/h.

Mechanical properties and density of BCxNy films grown by low-pressure chemical vapor deposition from triethylamine borane by V. R. Shayapov; M. L. Kosinova; A. P. Smirnov; E. A. Maksimovskii; B. M. Ayupov; Yu. M. Rumyantsev (262-266).
Boron carbonitride (BC x N y ) films of different compositions have been grown by low-pressure chemical vapor deposition using triethylamine borane as a single-source precursor and ammonia as an additional nitrogen source. Experiments were performed at various initial vapor compositions. The resultant films have been characterized by ellipsometry, IR spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, nanoindentation, and surface acoustic wave spectroscopy. The mechanical properties of the films are shown to correlate with their density and chemical composition. With increasing initial ammonia partial pressure in the vapor phase, the elemental composition of the films moves away from boron carbide, approaching boron nitride, which is accompanied by a reduction in the Young’s modulus, hardness, and density of the films.

Reactions of V2O5, Nb2O5, and Ta2O5 with AlN by V. M. Chumarev; V. P. Mar’evich; A. V. Larionov; A. Ya. Dubrovskii (267-272).
Reactions of vanadium, niobium, and tantalum pentoxides with aluminum nitride have been studied using X-ray diffraction. At temperatures from 1000 to 1600°C, we have identified various V, Nb, and Ta nitrides. The composition of the niobium and tantalum nitrides depends on the reaction temperature. The tendency toward nitride formation becomes stronger in the order V2O5 < Ta2O5 < Nb2O5.

We have studied the behavior of terephthalic acid (TPA) particles in sodium aluminate solutions. The results demonstrate that the addition of TPA to a solution at room temperature leads to appreciable TPA particle growth and the formation of amorphous aluminum hydroxide on the surface of the crystalline TPA floccules. With increasing initial aluminum concentration in solution, the interface displaces toward the central part of the floccules and an almost complete extraction of the dissolved aluminum is reached. The aluminate ion incorporation into the structure of TPA causes its conversion to an ionized form. In the resultant structure of amorphous aluminum hydroxide in TPA, the aluminum hydroxide crystallizes over time to form bayerite. Autoclaving in water vapor at 420°C produced boehmite ranging in crystallite size from 300 to 700 nm. Heat treatment in air for 2 h at 800°C leads to the formation of γ-Al2O3 in the form of spheres with a fiber length on the order of 300 nm and a thickness of 50–100 nm.

Synthesis of vanadium dioxide films by a modified sol-gel process by D. A. Vinichenko; V. P. Zlomanov; V. A. Vasil’ev; D. S. Seregin; O. Ya. Berezina (279-284).
Vanadium dioxide films have been grown on silicon substrates and on SiO2 layers on silicon by a modified sol-gel process using methyl cellosolve as a solvent. We have failed to obtain vanadium dioxide layers on Pt/TiO x /SiO2/Si substrates. For all of the substrates studied, we have examined the effect of synthesis conditions (initial solution concentration, deposition procedure, and oxidation and reduction anneals) on the phase composition, thickness, and surface morphology of the films.

Synthesis and luminescence properties of Eu2+-doped Li2SrSiO4 by S. M. Levshov; I. V. Berezovskaya; N. P. Efryushina; B. I. Zadneprovskii; V. P. Dotsenko (285-289).
We have studied the luminescence spectra of Li2Sr1 − x Eu x SiO4 (x = 0.0001–0.01) solid solutions prepared by solid-state reactions and a sol-gel process in a reducing atmosphere. The spectra show a broad band in the range 500–700 nm, centered at 578 nm, which is due to the 4f 65d → 4f 7 transition. The luminescence excitation spectrum shows, in addition to bands due to Eu2+ 4f 7 → 4f 65d transitions, a strong band centered at 174 nm, attributable to absorption in the SiO 4 4− group.

Phase relations in the TiO2-CsNO3 system between 550 and 1140 K by V. P. Kobyakov; T. V. Barinova; M. A. Sichinava (290-295).
We have studied reactions in the TiO2-CsNO3 system in the temperature range 550–1140 K in air using sample weight measurements, X-ray diffraction, electron microscopy, and electron probe microanalysis. The samples heat-treated at temperatures from 850 to 1140 K contained titanium cesium oxides.

Zr-based MCM-41 mesoporous molecular sieves (ZrMCM-41) were successfully synthesized by microwave irradiation method and hydrothermal method, respectively. The obtained samples were characterized by XRD, TEM, FT-IR and N2 physical adsorption. The results show that the samples synthesized by the two different methods both possess typical hexagonal mesoporous structure of MCM-41 and high specific surface areas (over 800 m2/g). After calcination at 750°C for 3 h or hydrothermal treatment at 100°C for 6 days, the mesoporous structure of the samples still retained, however, the mesoporous ordering is poor. Under the comparable conditions, the reaction time required in the synthesis of ZrMCM-41 by microwave irradiation method was greatly reduced, and microwave irradiation method is eco-friendly and is easy to operate.

Kinetics of lithium deintercalation from LiFePO4 by D. V. Safronov; I. Yu. Pinus; I. A. Profatilova; V. A. Tarnopol’skii; A. M. Skundin; A. B. Yaroslavtsev (303-307).
We have studied the kinetics of lithium deintercalation from lithium iron phosphate in a cathode material for batteries. The main contribution to the resistance of the cell is made by interfaces and the resistance of LiFePO4 grains. The FePO4 solubility in LiFePO4 is 4.0%. The lithium deintercalation process can be described in terms of a heterogeneous grain model and its rate is controlled by the lithium diffusion across the layer of the forming product (FePO4).

Effect of isovalent substitution on the structure and ionic conductivity of Li0.5 − y Na y La0.5□Nb2O6 by A. G. Belous; O. N. Gavrilenko; O. I. V’yunov; S. D. Kobilyanskaya; V. V. Trachevskii (308-312).
We have synthesized Li0.5 − y Na y La0.5□Nb2O6 defect perovskite solid solutions with 0 ≤ y ≤ 0.5. Their structure has been shown to undergo partial disordering with increasing sodium content. Lithium ion diffusion in the Li0.5 − y Na y La0.5□Nb2O6 system exhibits no percolation effects. The ionic conductivity as a function of sodium content has a maximum due to two competing factors: the increase in perovskite cell volume and the decrease in lithium ion concentration.

We have synthesized Ba1 − x (Zn1/2W1/2)O3 − x and Ba(Zn1/2 − y W1/2)O3 − y/2 barium tungstates with different deviations from cation stoichiometry (x = 0.01–0.05, y = 0.01–0.05), determined the phase composition of ceramics fabricated from the tungstates, and investigated their electrical properties. Even slight deviations from cation stoichiometry in Ba(Zn1/2W1/2)O3 lead to the formation of the scheelite phase BaWO4, and its content increases with heat-treatment temperature. Barium or zinc deficiency in the systems studied improves the sintering behavior of Ba(Zn1/2W1/2)O3 and increases the degree of 1: 1 B-site cation ordering, which in turn ensures an increase in microwave quality factor, Q.

The multicomponent refractory oxide system Zn2 − x (Ti a Zr b )1 − x Fe2x O4 (a + b = 1; a: b = 1: 5, 1: 4, 1: 3, 1: 2, 1: 1, 2: 1, 3: 1, 4: 1; x = 0–1.0; Δx = 0.05) has been studied by X-ray diffraction, using samples prepared by melting appropriate metal oxide mixtures in a low-temperature hydrogen-oxygen plasma. Two phases, both with wide homogeneity ranges, have been identified: α-phase, with a cubic inverse spinel structure, and β-phase, with a tetragonal inverse spinel structure. The phase boundaries in the system have been determined. Structural data are presented for about 100 solid solutions.

Mass spectrometric study of the thermodynamic properties of mixed-ligand Mn(III) complexes by N. N. Kamkin; A. I. Dement’ev; N. G. Yaryshev; A. S. Alikhanian; A. V. Kharchenko (324-328).
We have synthesized Mn(thd)3 (thd = dipivaloylmethane, or 2,2,6,6-tetramethyl-3,5-heptanedione) and evaluated its enthalpy of sublimation (89.0 ± 7.0 kJ/mol) and its saturated vapor pressure as a function of temperature from mass spectrometry data. Exchange reactions between Mn(acac)3 (acac = acetylacetonate, or 2,4-pentanedione) and Mn(thd)3 have been performed using an in situ technique. We have calculated the enthalpies of the exchange reactions and the enthalpies of formation of Mn(acac)2(thd) and Mn(acac)(thd)2 in the vapor phase: −1417.5 ± 15.0 and −1590.6 ± 15.0 kJ/mol, respectively.

Diffusion characteristics of surface-modified MK-40 mixed-cation ion-exchange membranes by Yu. A. Karavanova; K. G. Fedina; A. B. Yaroslavtsev (329-333).
Previously proposed approaches to determining diffusion parameters of mixed-cation membranes have been tested to describe ionic conductance and H+/M+ (M = Li, Na, K) interdiffusion data for asymmetric MK-40-based membranes modified with a thin layer of MF-4SK perfluorinated membrane material containing silica and zirconia additions. The diffusion coefficients, effective ion exchange constants, and asymmetry effects in the membranes are evaluated. The conclusion is made that there is an additional barrier to ion transport across the surface of MK-40 membranes.