Inorganic Materials (v.53, #9)

Metalorganic vapour phase epitaxy of GaAs/AlGaAs nanoheterostructures for a quantum cascade laser by A. A. Marmalyuk; A. A. Padalitsa; M. A. Ladugin; P. V. Gorlachuk; I. V. Yarotskaya; A. Yu. Andreev; T. A. Bagaev; A. V. Lobintsov; Yu. V. Kurnyavko; S. M. Sapozhnikov; A. I. Danilov; K. Yu. Telegin; V. A. Simakov; I. I. Zasavitskii; S. S. Zarubin (891-895).
Short-period GaAs/AlGaAs superlattices, an active region, and a quantum cascade laser heterostructure have been grown by metalorganic vapor phase epitaxy, and their characteristics have been studied by high-resolution X-ray diffraction, transmission electron microscopy, and photoluminescence spectroscopy. The heterostructures have been used to produce quantum cascade lasers emitting near 10 μm. Their output pulse power at 77 K is above 200 mW.
Keywords: metalorganic vapor phase epitaxy; superlattice; quantum cascade laser; GaAs/AlGaAs; mid-IR spectral region

Chemical interaction of InAs, InSb, GaAs, and GaSb with (NH4)2Cr2O7–HBr–C4H6O6 etching solutions by I. V. Levchenko; I. B. Stratiychuk; V. N. Tomashyk; G. P. Malanych (896-901).
This paper presents results on the kinetics and mechanism of the physicochemical interaction of InAs, InSb, GaAs, and GaSb semiconductor surfaces with (NH4)2Cr2O7–HBr–C4H6O6 etching solutions under reproducible hydrodynamic conditions in the case of laminar etchant flow over a substrate. We have identified regions of polishing and nonpolishing solutions and evaluated the apparent activation energy of the process. The surface morphology of the crystals has been examined by microstructural analysis after chemical etching. The results demonstrate that the presence of C4H6O6 in etchants helps to reduce the overall reaction rate and extend the region of polishing solutions.
Keywords: antimonides; arsenides; dynamic chemical polishing; etch rate; apparent activation energy

Synthesis and properties of a copper(I) cobalt(II) double sulfite by E. A. Chalaya; A. G. Tyurin; M. V. Vasekha; A. I. Biryukov; S. M. Sukharzhevskii (902-910).
The Pourbaix diagrams of the Cu–H2SO4–H2O and Co–H2SO4–H2O systems have been refined and the stability regions of sulfite phases in the diagrams have been identified. Phase diagrams of copper(I) copper( II) and copper(I) cobalt(II) double sulfites have been mapped out. The double sulfites Cu2SO3 · СuSO3 and Cu2SO3 · СoSO3 have been isolated from an aqueous solution saturated with sulfur dioxide. We have obtained electron paramagnetic resonance spectra of the double sulfite Cu2SO3 · СoSO3 and characterized it by X-ray diffraction, IR spectroscopy, particle size analysis, and thermogravimetry. A foundation has been laid for the thermodynamic prediction of the synthesis of the Cu2SO3 · MSO3 (M = Cu, Co) double sulfites.
Keywords: double sulfites; potential–pH phase diagram; Chevreul’s salt; electron paramagnetic resonance

Preparation and characterization of iron nanoparticles protected by an oxide film by M. I. Alymov; N. M. Rubtsov; B. S. Seplyarskii; V. A. Zelenskii; A. B. Ankudinov (911-915).
Iron nanopowders ranging in particle size from 20 to 100 nm have been synthesized by reducing a 1-mm-thick iron(III) hydroxide layer in flowing hydrogen at 400°C and then passivated for 6–60 min in flowing argon containing 3% air. Our results demonstrate that the passivated iron nanopowders do not oxidize in air for six months. The iron nanoparticles have been characterized by X-ray diffraction (crystallite size evaluation), Auger electron spectroscopy, and polymolecular adsorption. The passivated iron nanoparticles have been shown to consist of a metallic core and oxide shell 2–4 nm in thickness.
Keywords: nanopowder; iron; passivation; crystallite; Auger electron spectroscopy; polymolecular adsorption; metallic core

Reaction of metallic titanium with SiO gas by I. M. Belyaev; P. V. Istomin; E. I. Istomina (916-922).
We have studied the silicidation of thin VT 1-00 titanium strips in a gaseous SiO atmosphere at 1350°C. The results demonstrate that silicidation produces a porous layer of Ti5Si3Ox particles on the surface of the titanium strips. This is accompanied by the incorporation of oxygen atoms into the crystal lattice of α-titanium, resulting in the formation of an α-Ti〈Oy〉 (0.1 ≤ y ≤ 0.5) solid solution. The thickness of the Ti5Si3Ox layer and the oxygen concentration in the α-titanium lattice depend on the silicidation rate and time.
Keywords: SiO; silicidation; titanium; titanium silicides

Structure of the order parameter in iron pnictide-based superconducting materials by V. G. Yarzhemsky; A. D. Izotov; V. O. Izotova (923-929).
Using data on the crystal symmetry of iron pnictides, we have calculated possible symmetries of singlet two-electron states corresponding to the superconducting order parameter. It has been shown that the octet line node structure observed in photoemission spectra is due to interaction between pairs of the same symmetry and that the presence of an odd component of a superconducting state in NMR spectra is associated with states on the Brillouin zone boundary.
Keywords: high-T c superconductors; topological materials; order parameter

A [(Co40Fe40B20)34(SiO2)66/C]46 multilayer amorphous nanostructure, consisting of alternating metal-containing composite layers and carbon interlayers, has been grown on a rotating glass-ceramic substrate by ion-beam-sputtering two targets, one of which had the form of a metallic plate of the Co40Fe40B20 alloy with quartz inserts. The nonmetallic interlayers were grown by sputtering graphite (second target). In the multilayer nanostructure (MNS), the thickness (~4–8 nm) of the bilayers, consisting of the (Co40Fe40B20)34(SiO2)66 metal- and silicon oxide-containing composite layers and nonmetallic carbon interlayers, was determined by small-angle X-ray diffraction. Experimental data obtained by nondestructive depth profiling of the MNS using ultrasoft X-ray emission spectroscopy of the (Co40Fe40B20)34(SiO2)66 composite layers demonstrate that the composition of the dielectric component of the composite deviates from the stoichiometry of the quartz in the sputter target toward lower oxygen content, leading to the formation of the SiO1.7 suboxide. Fitting Si L 2,3 spectra with reference spectra of known phases indicates that the content of the silicon suboxide phase in the composition of the composite layers can reach half of the composition of the dielectric component, with the second half being SiO2. This circumstance can be favorable for increasing the role of a second carrier transport channel (granule–interlayer–granule) and contribute to the previously observed sharp drop in the resistivity and the overall rise in the magnetic permeability of the MNS.
Keywords: multilayer nanostructures; bilayer thickness; metal-containing composite layers; carbon interlayers; electronic structure; phase composition; silicon suboxide phases; small-angle X-ray diffraction; ultrasoft X-ray emission spectroscopy

Microhardness and fracture toughness of ZrO2–Sc2O3 solid electrolyte, doped with rare-earth and transition metals by A. V. Nikonov; A. S. Kaygorodov; K. A. Kuterbekov; K. Zh. Bekmyrza (937-943).
The influence of low concentrations (1 mol %) of co-dopants (Y, Ce, Gd, Er, La, Zn, Mn, Co and Cu) on the microhardness and fracture toughness of Zr0.81Sc0.19O2–δ (10.5ScSZ) solid electrolyte was studied by the indentation method. It was shown that co-doping of 10.5ScSZ by the rare-earth elements (Y, Ce, Gd, Er) results in microhardness increase on 4–45% due to stabilization of cubic phase in the grains, while the microhardness changing upon transition metals (Mn, Cu, Co, Zn) introduction is caused by the grain boundaries modification. The microhardness decreases on ~4 and 10% upon doping by Mn and Cu, accordingly, whereas the introduction of Co and Zn results in its increase approximately by 2 times. It was shown also that the influence of all investigated dopants on the fracture toughness is insignificant. The maximal effect observed for Cu was the fracture toughness increase from 2.1 up to 2.6 MPa m0.5.
Keywords: Sc2O3–ZrO2 solid electrolyte; ScSZ; doping; mechanical properties; microhardness; fracture toughness

Thermodynamic properties of Er2O3 · 2ZrO2 in the range 6–1400 K by P. G. Gagarin; A. V. Tyurin; V. N. Guskov; A. V. Khoroshilov; G. E. Nikiforova; K. S. Gavrichev (944-949).
The isobaric heat capacity of the Er2O3 · 2ZrO2 solid solution has been determined by adiabatic calorimetry and differential scanning calorimetry, and the enthalpy increment, entropy, and reduced Gibbs energy change of the solid solution have been calculated in the temperature range 6–1400 K with no allowance for the low-temperature (<6 K) magnetic transformations.
Keywords: erbium oxide; zirconium oxide; heat capacity

New, thermally stable Gd11(GeO4)(PO4)3O10-based upconversion phosphors by V. A. Krut’ko; M. G. Komova; D. V. Pominova (950-955).
A series of Gd11–xy Yb x Er y GeP3O26 germanate phosphates differing in the ratio of the Yb3+ and Er3+ active ions have been synthesized, and their luminescence spectra have been measured. According to X-ray diffraction characterization results, all of the synthesized germanate phosphates are single-phase and have a triclinic structure (sp. gr. P1). We have measured upconversion luminescence spectra due to the Er3+ 2H11/2, 4S3/24I15/2 and 4F9/24I15/2 radiative transitions in the synthesized gadolinium ytterbium erbium germanate phosphates and determined the luminescence upconversion energy yield (B en) in Gd11–xy Yb x Er y GeP3O26. The effects of the concentrations and ratio of the dopants in the Gd11(GeO4)(PO4)3O10 germanate phosphate host on B en and the ratio of the luminescence intensities in the red and green spectral regions (R/G) have been assessed.
Keywords: rare-earth germanate phosphates; coprecipitation synthesis; infrared excitation; upconversion phosphors; energy yield

Heat capacity of rare-earth stannates in the range 350–1000 K by L. T. Denisova; Yu. F. Kargin; V. M. Denisov (956-961).
R2Sn2O7 (R = Pr–Lu) rare-earth stannates with the pyrochlore structure have been synthesized by solid-state reactions, by firing stoichiometric mixtures of SnO2 and R2O3 in air at 1473 K. The high-temperature heat capacity of the rare-earth stannates has been determined by differential scanning calorimetry in the temperature range 350 to 1000 K, and the Raman spectra of polycrystalline Tb2Sn2O7 and Dy2Sn2O7 samples have been measured.
Keywords: rare-earth stannates; structure; high-temperature heat capacity; thermodynamic functions

Fluorination of Bi1.8Fe1.2SbO7 pyrochlore solid solutions by A. V. Egorysheva; O. G. Ellert; O. M. Gaitko; M. N. Brekhovskikh; I. A. Zhidkova; Yu. V. Maksimov (962-968).
A technique has been developed for fluorinating the pyrochlore oxide Bi1.8Fe0.2FeSbO7, and a compound with the composition Bi1.8Fe1.2SbO7–x/2Fx has been obtained. The synthesized oxyfluoride also has the pyrochlore structure (sp. gr. Fd3m), with a lattice parameter a = 10.4443(1) Å (R wp = 5.2). It has been shown that the charge balance upon fluorine substitution for oxygen is maintained not through partial reduction of Fe3+ to Fe2+ but through the incorporation of fluorine into oxygen vacancies. The magnetic behavior of the fluorinated pyrochlore phase is determined by the persisting frustration of the octahedral sublattice, which is responsible for the development of a spin glass state below T f = 12 K. The fluorination-induced changes in the anion sublattice led to an increase in the antiferromagnetic exchange interaction between neighboring Fe3+ ions and changes in the dynamic properties of the spin glass phase.
Keywords: pyrochlore; fluorination; magnetic frustration

Molecular composition of organic impurities in extrapure sulfur by M. F. Churbanov; G. E. Snopatin; A. Yu. Sozin; I. V. Skripachev (969-972).
We have determined the molecular composition of organic impurities in extrapure sulfur obtained by the distillation purification of sulfur recovered from gaseous hydrocarbons. Using vacuum extraction, we obtained a concentrate of impurities highly volatile compared to the major component. Gas chromatography/ mass spectrometry analysis indicated the presence of impurities in the form of hydrocarbons with up to eight carbon atoms and their thio, oxy, and nitro derivatives. The detection of this group of impurities accounts for the distinctive features of the preparation of sulfur with low carbon and oxygen contents through ultrapurification of gas-derived sulfur.
Keywords: sulfur; purification; hydrocarbons impurities

We have studied the effect of water glass prepared by a wet-chemical process on the principal properties of structural materials using alkali-activated mineral binders and determined the optimal hydrothermal leaching time for tripoli, corresponding to the maximum SiO2 concentration in the water glass slurry. We have investigated the initial structure of the tripoli and the leaching-induced structural changes in its mineral component. The influence of three types of mixing agents has been analyzed in the context of the preparation of materials: water glass in the form of slurry, water glass slurry filtrate, and the filtered-off insoluble residue of the slurry in the form of thick mass. The strength of the obtained materials increases in the following order: insoluble residue < filtrate < slurry. The present results demonstrate that the materials have high strength characteristics and that water glass prepared by a wet-chemical process is potentially attractive for practical application.
Keywords: water glass; tripoli; alkali activated

Evolution of the microstructure and phase composition of materials based on the fluorohydroxyapatite–zirconia–alumina system during sintering by V. V. Smirnov; A. I. Krylov; S. V. Smirnov; M. A. Goldberg; O. S. Antonova; T. O. Obolkina; A. A. Konovalov; S. M. Barinov (980-986).
We have studied the influence of the sintering temperature, Al2O3 additions, and liquid-forming sintering aids on the phase composition and microstructure of fluorohydroxyapatite-based composite ceramic materials containing 20 and 60% zirconia. The addition of alumina has been shown to prevent secondary recrystallization processes during sintering and contribute to stabilization of tetragonal zirconia. The addition of the sintering aid has made it possible to lower the sintering temperature to 1200°C.
Keywords: bioceramics; zirconia; fluorohydroxyapatite; alumina; sintering

This paper examines the feasibility of using electrophoretic deposition for producing thin films of cathode materials based on lanthanum nickel oxides (with the lanthanum nickelate La2NiO4 + δ (LNO) as the predominant phase). We have determined the particle size and zeta potential of nonaqueous suspensions of LNO micro- and nanopowders prepared by solid-state reactions, pyrolysis of liquid precursors, and laser evaporation of a target. Using ultrasonic processing, we have obtained stable LNO nanopowder suspensions in acetylacetone and an isopropanol + acetylacetone mixture, which have zeta potentials of +25 and + 38 mV, respectively. Electrophoretic deposition on a dense model cathode has produced thin bilayer coatings from electrode and electrolyte materials (LNO and Се0.8(Sm0.75Sr0.2Ba0.05)0.2O2–δ), which are of interest for solid oxide fuel cell technology.
Keywords: nanopowders; electrode materials; electrophoretic deposition

Sol–gel synthesis of Ta2O5–SiO2 composites from tantalum(V) chloride and tetraethyl orthosilicate in ethanol by A. G. Mal’chik; S. A. Kuznetsova; S. O. Kryuchkova; V. V. Kozik (994-1003).
Ta2O5–SiO2 composites containing 10, 50, and 90 wt % SiO2 have been prepared by a sol–gel process in ethanolic solutions of tantalum(V) chloride with tetraethyl orthosilicate. The physicochemical aspects of their formation have been studied by IR spectroscopy, X-ray diffraction, X-ray microanalysis, and thermal analysis in combination with mass spectrometry. The results demonstrate that the SiO2 content of the Ta2O5–SiO2 composites influences the uniformity of the tantalum and oxygen distributions on the surface of the materials and that heat-treatment conditions influence their crystallinity.
Keywords: sol–gel synthesis; tantalum(V) oxide; silicon oxide; Ta2O5–SiO2 composites