I. Ya. Mittova

Synthesis and magnetic properties of YFeO3 nanocrystals

YFeO3 nanocrystals have been prepared via coprecipitation of yttrium and iron(III) chlorides with aqueous ammonia. The average size, morphology, and magnetic properties of the YFeO3 nanoparticles are shown to be highly dependent on the preparation procedure.

Solid-phase interaction in the hydroxyapatite/titanium heterostructures upon high-temperature annealing in air and argon

Samples of 100- and 500-nm-thick hydroxyapatite films on titanium were investigated using scanning electron microscopy, electron probe X-ray microanalysis, and X-ray powder diffraction. The films were prepared by high-frequency magnetron sputtering of a target in an argon atmosphere (1 × 10−1 Pa) at a magnetron power density of 40–70 W/cm2. These conditions provided growth of films at a rate as high as 0.7 nm/s. It was demonstrated that the hydroxyapatite film annealed in argon is characterized by deep pores that have diameters ranging from 0.3 to 8.0 µm and are uniformly distributed throughout the film surface. The electron probe X-ray microanalysis confirmed the presence of all elements (Ti, O, Ca, P) under investigation, except for hydrogen, in the samples of the films. For biologically compatible hydroxyapatite, the optimum ratio Ca : P ≃ 1.5–1.7 was achieved in the hydroxyapatite/titanium system with a 500-nm-thick hydroxyapatite layer upon annealing in argon at a temperature of 1050°C for 30 min. It was established that the hydroxyapatite/titanium system contains intermediate phases, including calcium titanate CaTiO3, which proved the interaction of hydroxyapatite with titanium.

Influence of lanthanum content and annealing temperature on the size and magnetic properties of sol–gel derived Y1 − xLaxFeO3 nanocrystals

Y1 − xLaxFeO3 (x = 0, 0.1, 0.2, 0.3, 0.4) nanocrystals have been prepared by a sol-gel process. With increasing lanthanum content (x from 0 to 0.4), their size decreases significantly (from 34 to 16 nm), whereas their magnetization increases. Raising the annealing temperature increases their size.

Vaporization and thermodynamic properties of the PbO-V2O5 system

The vaporization of individual lead and vanadium oxides and a wide range of compositions of PbO-V2O5 melts has been studied. The thermodynamic characteristics of the PbO-V2O5 system have been determined, PbO-V2O5 melts show negative deviations from the ideal behavior because of the formation of thermally stable compounds in their condensed phase. For gaseous lead vanadate PbV2O6, the thermodynamic functions have been calculated and the standard enthalpies of formation and atomization have been determined.

Synthesis and magnetic properties of nanocrystalline Y1 − xCdxFeO3 − δ (0 ≤ x ≤ 0.2)

We report the synthesis of Y1 − xCdxFeO3 − δ nanocrystals in the range x = 0–0.2. The Y1 − xCdxFeO3 − δ materials were shown to be single-phase by X-ray diffraction, with an average crystallite size from 23 to 34 nm, depending on composition. With increasing cadmium oxide content, the size of the Y1 − xCdxFeO3 − δ nanocrystals decreases and their magnetization rises.

Influence of the preparation conditions on the size and morphology of nanocrystalline lanthanum orthoferrite

Nanocrystalline LaFeO3 is prepared by the dehydration of coprecipitated lanthanum and iron(III) hydroxides. It is shown that the behavior of the samples during heating and the size distribution of LaFeO3 nanocrystals can be considerably different depending on the scheme used for coprecipitation of lanthanum and iron hydroxides; independently of the method employed for coprecipitation of the initial compounds, sintering of the samples at 950°C leads to the formation of lanthanum orthoferrite crystals up to 100 nm in size.

Influence of the synthesis conditions on the particle size and morphology of yttrium orthoferrite obtained from aqueous solutions

The size and morphology of yttrium orthoferrite nanoparticles were examined in relation to the synthesis conditions. The chemical composition of the crystalline phases resulted from heat treatment of the samples at 650°C varies with the procedure of coprecipitation of yttrium and iron(III) hydroxides. At the same time, heat treatment at 750°C leads to formation of yttrium orthoferrite solely. The size of the YFeO3 crystals is weakly dependent on the initial composition preparation procedure, and the size and shape of their agglomerates are sensitive to the conditions of coprecipitation of the hydroxides.

Growth of vanadium oxide films on InP under mild conditions and thermal oxidation of the resultant structures

Techniques have been developed for producing vanadium oxide films (10 nm to 1 μm thick) on indium phosphide using vanadium(V) oxide gels and sols through immersion and deposition from aerosol. Using scanning tunneling microscopy and X-ray diffraction, we have studied the influence of annealing temperature and time on the morphology and composition of the films and the influence of the films on the thermal oxidation of InP.

Sol-gel formation and properties of nanocrystals of solid solutions Y1 − xCaxFeO3

Nanopowders of ferrites Y1 − xCaxFeO3 (x = 0.1, 0.2, and 0.3) were prepared by chemical coprecipitation of cations Y3+, Ca2+, and Fe3+ by an aqueous sodium carbonate solution. It was found that an increase in the calcium content leads to a decrease in the size of nanocrystals, the average size of which is 25–50 nm. Doping of yttrium orthoferrite with the doubly charged calcium ion enhances magnetization and decreases coercivity in samples.

High-speed determination of the thickness and spectral ellipsometry investigation of films produced by the thermal oxidation of InP and V x O y /InP structures

Spectral ellipsometry was used to determine the thickness and optical properties of films produced by the thermal oxidation of InP and VxOy/InP structures. Comparison of the measured optical characteristics and thickness of nanofilms with high-speed ellipsometric analysis data indicates that the two methods should be used in the case of multicomponent films. Absorption in such films is shown to be due, among other factors, to the presence of unoxidized indium, which influences the optical properties of the film and the ellipsometric measurement results.