Comparative studies of alloys of the Sm – Co – Cu – Fe – Zr system fabricated by vacuum induction melting from pure blend components and recoverable resources are performed. The results of the scanning and transmission electron microscopy, local chemical analysis, x-ray phase analysis and other studies show that the chemical and phase compositions of the hard magnetic alloys are virtually identical. The magnetic properties of the samples obtained from recoverable resources and pure components correspond to alloy KS25DTs210 in accordance with GOST 21559–76. This means that the use of recycled materials is permissible from the standpoint of formation of demanded magnetic properties and matches an economically efficient, resource-saving and nonwaste technology.

Crystals of fluorite phases with the CaF2 structure: Ba1-xLaxF2+x (x = 0, 0.05, 0.105, 0.25, 0.35, 0.40) and those of tysonite ones with the LaF3 structure: La1-yBayF3-y (y = 0, 0.05, 0.09) have been studied by electron diffraction and elemental analysis in a transmission electron microscope. Diffraction patterns of Ba1-xLaxF2+x crystals with x = 0.105, 0.25 exhibit diffuse scattering, which indicates the presence of clusters of structural defects. Blurred supercell reflections are seen in diffraction patterns of Ba1-xLaxF2+x crystals with a high lanthanum content (x = 0.35, 0.40) in addition to diffuse scattering. They indicate the existence of nanoscale ordered crystallites as well as clusters. It was found that LaF3 and the tysonite phase La1-yBayF3-y with a low barium content (y = 0.05) is of a low-temperature l-form (space group P (3) over bar c1, Z = 6). A small fraction of tysonite crystallites in La1-yBayF3-y crystals with y = 0.09 is of a high-temperature h-form (space group P6(3)/mmc, Z = 2). An intermediate crystal structure between l- and h-forms was also found. The maximum ionic conductivity sdc of tysonite crystals La1-yBayF3-y at 293 K is 800 times higher than that of fluorite ones Ba1-xLaxF2+x. A correlation was found between logarithm of conductivity and composition: lg sigma(dc)(x) = ax + b for fluorite Ba1-xLaxF2+x and tysonite La1-yBayF3-y crystals. The reason for the additive law of change in ionic conductivity in both types of nonstoichiometric phases in the BaF2-LaF3 system is apparently the similarity of defect structures of fluorite and tysonite phases.

Comparative studies of alloys of the Sm - Co - Cu - Fe - Zr system fabricated by vacuum induction melting from pure blend components and recoverable resources are performed. The results of the scanning and transmission electron microscopy, local chemical analysis, x-ray phase analysis and other studies show that the chemical and phase compositions of the hard magnetic alloys are virtually identical. The magnetic properties of the samples obtained from recoverable resources and pure components correspond to alloy KS25DTs210 in accordance with GOST 21559-76. This means that the use of recycled materials is permissible from the standpoint of formation of demanded magnetic properties and matches an economically efficient, resource-saving and nonwaste technology.

The morphology and structure of cobalt-containing nanoparticles Co2B on the surface of polystyrene microgranules have been investigated by a set of structural methods, including X-ray diffraction, electron diffraction, and transmission electron microscopy. It has been established that the nanoparticles are 30–100 nm in size and have a spherical or pentagonal shape. It is shown that the nanoparticles have a cluster structure with an individual cluster size of several nanometers. The growth of pentagonal Co2B nanoparticles on the microgranule surface may be due to the processes similar to those occurring in wildlife during the formation of organisms and plants of pentagonal shape.

The process of interaction of graphene with iron oxide nanoparticles was investigated. First, graphene oxide (GO) modified with magnetite Fe3O4 nanoparticles was successfully synthesized. Raman and MOssbauer spectroscopy revealed that the magnetite Fe3O4 in combination with GO became non-stoichiometric, and the maghemite phase gamma-Fe2O3 appears. Subsequent reduction of graphene oxide by thermal treatment leads to an increase in the fraction of maghemite content and, in addition, the hematite phase alpha-Fe2O3 appears in the sample annealed at above 500 degrees C. Meanwhile, the core-shell nanocomposites of FexOy/G appear, were FexOy consists of a mixture of the Fe3O4, gamma-Fe2O3 and alpha-Fe2O3 phases. The content of each phase can be varied by the annealing temperature. Magnetic, Mossbauer and Raman spectroscopy measurements indicate that graphene can interact with iron oxide. Charge-transfer from iron to graphene can occur due to delocalization of 3d electrons, which reduces the overall magnetic moment of the charge -transfer complexes. These properties can have potential applications in electronic such as supercapacitors, advanced anode materials for lithium-ion batteries, magnetically targeted drug delivery, photothermic therapy, and magnetic resonance imaging.

The composition and the structure of ceramic EuBa2Cu3O6 + δ (Eu-123) oxide samples annealed in steps with varying processing conditions (in air or oxygen and argon atmosphere at a temperature of 940–960°С for 1–70 h with or without homogenization) were studied by the X-ray phase and chemical analysis, electron diffraction pattern analysis, elemental analysis, and high-resolution transmission electron microscopy. Regardless of the processing conditions, Eu-123 nanostructured oxide with a tetragonal or orthorhombic structure and domains 1–20 nm in size was obtained as a result of annealing. Nanostructuring of the samples, which was revealed by high-resolution electron microscopy, is attributed to their chemical nature: the presence of identical structural elements in members of the homologous Eu n Ba m Cum + nO y series of oxides allows them to intergrow coherently and create an illusion of a single crystal. Just like any other member of the Eu n Ba m Cum + nO y series, oxide Eu-123 is disproportionate depending on the annealing conditions to form other members of this series located on either side of the dominant oxide. Temperature Tc of the superconducting transition of each member of the series depends on the average oxidation state of copper \(\overline {Cu} \). At \(\overline {Cu} \) < 2, all members of the series have a tetragonal structure and do not exhibit superconducting properties. At \(\overline {Cu} \) = 2.28, five members of the Eu n Ba m Cum + nO y series with matrices (Ba : Cu) 5 : 8, 3 : 5, 2 : 3, 5 : 7, and 3 : 4 exhibit superconducting properties with Tc = 82–90 K.

Powder and polycrystals synthesized from Ga, Se, Er components, as well as GaSe and GaSe:Er single crystals grown from melt in argon atmosphere and in vacuum, respectively, are studied. The growth and quenching conditions used in this work provide 2.5 times increase in solubility of erbium in GaSe matrix and a decrease in number of phases to GaSe and Er2Se3, oppositely to multiphase GaSe:Er alloys known from literature. For the first time Er2Se3 phase was detected by XRD in GaSe crystal doped with 1 at%Er. Possible orientation relations are derived for Er2Se3/GaSe epitaxial pair. It has been shown that stretched reflections in electron micro diffraction patterns and scattering of maximums in x-ray diffraction patterns are bound to stacking faults, which appear owing to thin interlayers of 8-GaSe polytype in epsilon-GaSe matrix of the melt-grown crystals. Morphology of growing crystal surface is studied. Photoluminescence spectra of pure and erbium-doped GaSe display intense photoluminescence bands, which are, presumably, associated with defect states in band gap of GaSe. It is shown that doping with Er has a strong effect on photoluminescence intensity and on its spectral composition. The measured 1.7 times increase in Vickers microhardness (up to 400 MPa) with respect to pure GaSe is due to solid solution hardening and to precipitation.

Cobalt nanoparticles (3–7 nm in size) obtained by cobalt carbonyl decomposition in 1,2-dichlorobenzene in the presence of surfactants (trioctylphosphine oxide and oleic acid) have been studied by a complex of structural methods: small-angle X-ray scattering, electron diffraction, and transmission electron microscopy. The nanoparticles synthesized are found to consist of the cubic ε-Со phase; their crystal structure is described within the sp. gr. P4132, a = 6.097 Å. Using small-angle X-ray scattering, the size and shape of nanoparticles have been determined directly in the liquid dispersion. Most of the particles have a spherical shape; their average size is ≈3.5 ± 0.5 nm, which agrees with the electron microscopy data. Possible factors causing the ε-phase formation during synthesis of metallic Co nanoparticles are discussed.

Phase composition of La1−ySryF3−y (y=0, 0.05, 0.0725, 0.10, 0.15) crystals with the tysonite-type (LaF3) structure has been studied by electron diffraction and elemental analysis in a transmission electron microscope. Lamellar inclusions of the impurity phase with thickness~20Å were detected in the (y=0.10, 0.15) crystals. The impurity phase apparently has a fluorite-based structure. The interrelation between decreasing F-ionic conductivity of the La1−ySryF3−y samples after its maximum (at composition≈La0.95Sr0.05F2.95) with increasing alkaline-earth element content and formation of nm-sized inclusions of the impurity phase has been established. Formation of the impurity phase taking place at the expense of the conducting tysonite phase reduces the percentage of the latter phase in the samples, while inclusions of the impurity phase blockade pathways for mobile fluorine ions.

Electron diffraction combined with simultaneous analysis of elemental composition in a transmission electron microscope is used for the first time to investigate La1–y Sr y F3–y (0 ≤ y ≤ 0.15) phases with tysonite structure (LaF3). The two-phase structure of samples with y = 0.10 and 0.15 containing a tysonite matrix and thin interlayers of a phase with a structure similar to that of sphalerite is revealed. The two-phase state is presumably also present in a sample with y = 0.075; however, its content of the platelike phase is too small to be detected via electron diffraction. The presence of the platelike phase in the samples with y = 0.075, 0.10, and 0.15 explains the drop in fluorine ionic conductivity from its maximum at y = 0.05.

Samples of high-temperature superconducting oxide EuBa2Cu3O6 + δ (Eu-123) with total cationic composition Eu: Ba: Cu = 1: 2: 3 are investigated by means of local X-ray microanalysis and high-resolution transmission electron microscopy. The cationic nonstoichiometry of Eu-123 oxide is revealed. The particles of the studied samples are inhomogeneous in structure on the nanoscale, with two types of inhomogeneities: one with typical sizes of one to several nanometers, and one with typical sizes of 10 to 20 nm, respectively.

A YBa2Cu3 O (6.92) superconductor has been studied in an aberration-corrected scanning transmission electron microscope using a combination of atomic resolution imaging and elemental mapping by electron-energy loss spectroscopy (EELS). YBa2Cu3 O (6.92) has been found to be of a nanostructural state due to local variation of cation composition on a nanometer-sized scale. YBa2Cu3 O (6.92) can thus be considered as a non-single phased material formed of coherently intergrown nanodomains of phases with different cation compositions.

A phase analysis of 11 samples of the CaF2–ErF3 system in the range of 65–85 mol % CaF2 is performed by means of transmission electron microscopy (TEM) and X-ray elemental analysis. The specimens are synthesized at 905 ± 10°C for 230 h and quenched at a rate of ~200 grad s–1. An ordered phase with a fluorite structure and a composition close to Ca0.6Er0.4F2.4, an ordered phase that is a derivative of a tysonite structure with a composition close to Er0.7Ca0.3F2.7, and ErF3 are revealed, along with a phase having a variable composition of 73–78 mol % ErF3. The latter phase has a tysonite matrix and embedded nanometersized lamellar inclusions of a phase that likely inherited the structure of an ordered phase.