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Sr2FeMoO6–δ single-phase samples without Fe/Mo cations superstructural ordering (P) and with Curie temperature 407 K were obtained by the solid-phase technique. According to the XRD data, the growth dynamics of the parameter P is nonlinear. In this case, the process of reaching maximum values of P (Pmax) is long and its rate is several times lower than the change of the oxygen index 6–δ. It was found that with increasing temperature of isothermal annealing, P increases and reaches maximal values 88 % at T = 1320 K for 120 h, Pmax = 92 % at T = 1420 K for 100 h, while Pmax = 90 % at T = 1470 K for 45 h. One can assume that the lower values of Pmax at T = 1470 K than at T = 1420 K are due to the influence of thermal energy on the destruction of chain ordering of Fe and Mo cations placed in staggered order. Based on the analysis of P time dependences, two relaxation processes can be found and the dP/dt = ¦(t) can be divided into two regions – I and II. In the region I the relaxation time is shorter than that in the region II. The point is that the ordering of cations in the –O–Fe–O–Mo–O chains in the region I requires atomic displacements by approximately one interatomic distance, whereas in the region II cation displacements occur over long distances with the formation of long[1]chain long-range ordering.

The kinetics of phase contents modification in the process of SrBaFeMoO6–δ crystallization from a stoichiometric mixture of SrCO3 + BaCO3 + 0,5Fe2O3 + MoO3 simple oxides using the solid phase method has been investigated. In the temperature region of 300–1200°С, a number of endotermic effects have been detected. Herewith, the first one (with maximum around 552°С) and the third one (with maximum around 743°С) are accompanying by the significant decrease of the mass of specimen. In the temperature range of 946–1200°С, the mass change of specimen is practically not observable, while the thermal effect is still present, and the specimen remains not single-phase one. This indicates the difficulty of the flow of solid phase reactions with the formation of solid solution of barium-strontium ferromolybdate. During analysis of the change of the phase composition consisting of a mixture of initial reagents of stoichiometric relation SrCO3 + BaCO3 + 0,5Fe2O3 + MoO3, it has been observed that with increasing temperature, complex compounds BaMoO4, SrFeO3 appear almost simultaneously, then SrBaFeMoO6–δ appears consequently. Thus, the compounds BaMoO4 и SrFeO3, are structure forming for the solid solution of barium-strontium ferromolybdate. With further temperature increase up to 770°С the formation of new compound ВаFeO3 with disappearing SrFeO3 was detected. In this case, the amount of double perovskite increases faster than that of barium molybdate. The main accompanying compounds at the crystallization of the SrBaFeMoO6–δ double perovskite solid solution are BaMoO4 and SrFeO3. It was established that at the initial stage of the interaction, the resulting solid solution of barium-strontium ferromolybdate is enriched with iron and its composition changes during the reaction in the direction of an increase of the molybdenum content, as in the case of other precursor combinations.

The metal oxide compounds Sr2FeMoO6–d systems with an ordered double perovskite structure due to their unique and extremely important magnetotransport and magnetic properties are among the most promising materials for spintronic devices. In the present work, we investigated the correlation between the citrate-gel synthesis conditions (pH of initial solutions and annealing temperature) and the microstructure, phase transformations and magnetic properties of the Sr2FeMoO6–d nanopowders. According to the results the average grain size of the powders in the dispersion grows from 250 to 550 nm with increasing of pH values. Single-phase nanosized Sr2FeMoO6–d powders had various degrees of superstructural ordering of Fe3+ and Mo5+ (P = 65% for pH = 4, P = 51% for pH = 6 and P = 20 % for pH = 9). With increasing of pH, the Fe2+ concentration increases from 63% to 72%, and the Fe+3 concentration drops from 37% to 28%. According to the results of investigations of magnetization temperature dependence in Sr2FeMoO6–d powders a metastable superparamagnetic state was established at TS

Ceramic piezomaterials based on Pb0.75Ba0.15Zr0.53Ti0.47O3 (PBZT) system are characterized by high values of the ferroelectric Curie temperature and polarization. They have widespread applications in electromechanical and electroacoustic transducers, bandwidth filters, transformers, frequency stabilized resonators, etc. Preparation of PBZT composites with nano-inclusions of Cu and Ni have been carried out by a complex powder technology including metallization procedures which were performed by the well-known chemical deposition method from standard solutions of copper and nickel. Studies of hydrostatic density and porosity of obtained samples as well as their microstructural investigations have yielded a larger density of PBZT-metal composites (5.3 – 7.3 g/cm3) as compared with pure PBZT (4.7 g/cm3). Measurements of dielectric properties of samples in the frequency range from 20 Hz – 1 MHz have shown that the Curie temperature increases in PBZT (Ni) and decreases in PBZT(Cu) in comparison with pure PBZT. The complex dielectric permittivity of all investigated composites at higher temperatures and low frequencies is mainly caused by the high electrical conductivity. Only at the highest frequency used (1 MHz) the real part of the complex permittivity is caused by a resonant soft mode and could be fitted with the Curie-Weiss law. The activation energy of ferroelectric domain mobility in PBZT (Cu, Ni) composites is lower than in pure PBZT. This can be explained by a decrease of the domain size in composites. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The present paper shows that inhomogeneity in magnetic structure of Sr2FeMoO6–δ metal oxide compounds, that essentially depends on synthesis conditions, leads to different degrees of superstructural ordering of Fe3+ and Mo5+ cations. According to the temperature dependence of magnetization measured in the absence of a magnetic field, the sharp jump in the low temperature region (2.3–23 K) indicates the existence of magnetic fields with low coercivity, where the superparamagnetic state is realized. It has been established that magnetic inhomogeneity of antiferromagnetic-ferromagnetic materials promotes a frustration of the exchange coupling and facilitates a realization of the spin glass state in the material. A decrease of magnetic inhomogeneity and the corresponding increase in the degree of superstructural ordering of cations cause the negative magnetoresistivity effect to increase up to 14%, and to be unchanged at temperatures below 15 K.

Light-attenuation spectra of yttrium–iron garnet single-crystal film structures grown on a gallium–gadolinium garnet substrate by liquid-phase epitaxy from the undercooled solution in the melt have been studied and compared with those of bulk yttrium–iron garnet samples. The calculated optical constants are discussed taking into account the influence of crystal field on the splitting of the energy states of iron ions in the film samples.

Methods of growth of KTiOPO4 and K1 − xRbxTiOPO4 crystals of high optical quality have been optimized. The dielectric properties (permittivity and conductivity) of the crystals grown have been investigated at frequencies from 102 to 106 Hz in the temperature range from 100 to 350 K, along the [001] crystallographic direction. It is established that partial substitution of K+ ions with Rb+ ions leads to a decrease in the permittivity and conductivity.

Based on the data of X-ray phase and microstructure analysis, the sample composition was optimized in order to provide maximum size of the textured macrograins of YBa2Cu3O7-δ and of the crystallites in the Y2BaCuO5-BaCuO2-CuO, Y2Cu2O5-BaCuO2 systems. The growth rate has been studied and the YBa2Cu3O7-δ growth activation energy has been calculated for the samples of Y2BaCuO5+3BaCuO2+2.3CuO, Y2BaCuO5+3BaCuO2+0.6CuO, and Y2Cu2O5+3.5BaCuO2 compounds in the temperature range of 1240-1270K for the case of use of the Y2Cu2O5 and Y2BaCuO5 precursors with an average grain diameter of 10 μm and 1mm. A crystallization mechanism of YBa2Cu3O7-δ in the Y2BaCuO5-BaCuO2-CuO and Y2Cu2O5-BaCuO2 systems in the case of different sizes of Y2BaCuO5 and Y2Cu2O5 precursor grains was proposed and validated. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Strontium ferromolybdate (Sr2FeMoO6-delta, SFMO) is a material exhibiting promising magnetoresistive properties. We have synthesized SFMO samples out of simple oxides (SrCO3, Fe2O3, and MoO3) or partially reduced SrFeO3-x (SFO) and SrMoO4-y (SMO) precursors. The samples have been experimentally investigated using X-ray diffraction, temperature-dependent magnetization, Mossbauer effect and ferromagnetic resonance measurements. Samples of the first type contain a high density of defects, especially [Fe-Mo], [Mo-Fe] antisites, and do not exhibit any superstructural ordering of the iron and molybdenum ions (P=0%). These samples comprise iron cations in a mixed valence state, Fe2+/3+, and are characterized by a higher magnetic inhomogeneity than those synthesized out of precursors. The use of the latter increases the sample density and brings about a growth acceleration, synthesis temperature reduction, as well as the appearance of a superstructural ordering of the Fe3+ and Mo5+ cations with P=64%. The samples exhibit magnetic anisotropy and consist of nanosize grains. Zero-field-cooling measurements of the temperature dependences of the magnetization reveal a sudden leap of the magnetization at low temperatures (below 23 K) that witnesses the existence of magnetic regions with a low coercivity, in which a superparamagnetic state exists. The obtained results are important for the optimization of the synthesis technology of SFMO for device applications.

The results of the coulometric study of the processes of oxygen sorption–desorption in optical coatings (OCs) of the SiO2- δ system deposited by the electron-beam sputtering technique are presented. The character of structural transformations occurring when the coatings under-go polythermal annealing within the temperature range from 200 to 1000°C and at oxygen partial pressures p O2=102–105 Pa has been established. It has been ascertained that the intensity of photoluminescence of the OCs and shift of the absorption edge depends on the annealing condition within the temperature range from 400 to 550°C in the dehydrated oxygen atmosphere that is caused by the coagulation of silicon atoms with their subsequent oxidization. The dependence of the optical damage thresholds of the SiO2- δ on structural defects has been studied.

Comparable studies of phase composition, dispersity and magnetic properties of Sr2FeMoO6 powders obtained by the solid-phase synthesis and the modified sol-gel method have been carried out. The powder obtained by the solid-phase synthesis has high phase purity with the concentration of antistructural defects of 17%. The sol-gel synthesis allows obtaining the large fraction of nanoparticles (≥ 60%) with highly coercitive magnetic inclusions.

The sequence of the different phase layers in reaction zones of the Y2BaCuO5-BaCuO2, Y2Cu2O5-BaCuO2, Y2Ba4O7-CuO diffusion couples has been established at 930–950°C in air. The Y, Ba, Cu distributions over the zones have been determined by electron microprobe analysis (EMA), and diffusion path has been plotten into isothermal section of the phase diagram. The number and the width of intermediate layers give informations about the synthesis of YBa2Cu3O7−δ superconducting phases.

It is determined that the state of initial reagents considerably influence the inhomogeneity of Sr 2 FeMoO 6−δ samples microstructure which has caused the appearance of super-paramagnetism and spin glass state in Sr 2 FeMoO 6−δ .

The influence of grain sizes of SrFeO3 and SrMoO4 precursors on phase transitions sequence, and Fe3+and Mo5+ cations ordering in Sr2FeMoO6-delta is investigated.