Competitive economic indicators for fast-neuron power reactors can be achieved with high coefficients of fuel burnout, which requires remarkable enhancement of radiation resistance of fuel pin claddings. Nowadays, low-activation vanadium alloys are projected as promising fuel cladding materials in view of their high radiation and thermal resistance in wide temperature and damage dose ranges. Neutron diffraction and small-angle neutron scattering are employed to study the microstructure of the V-4Ti-4Cr alloy subjected to irradiation with fast neutrons in the fluence range up to 1·1020 cm−2. Minor phases precipitated in the system are structurally characterized. The applicability and prospects of neutron diffraction methods in terms of studying the radiation behavior of this kind of alloys are shown.

Neutron diffraction and soft X-ray absorption spectroscopy have been applied for studying crystal structure, charges, and spin states of cobalt ions in nonstoichiometric Tb1−yBa1+yCo2−xO5.5−δ cobaltites. The following single-phase samples with defects in anion and cation sublattices were synthesized and investigated: TbBaCo2O5.38, TbBaCo1.95O5.31, TbBaCo1.90O5.24, and Tb0.95Ba1.05Co1.90O5.21. Co and Tb charge states have been estimated from soft X-ray absorption spectra. The anisotropic nature of changes of lattice parameters depending on the content of cobalt and oxygen vacancies has been established. A correlation between cobalt and oxygen vacancies in double layered cobaltites and a role of apical and planar oxygen in the formation of the Tb1−yBa1+yCo2−xO5.5−δ structure have been shown. Oxygen vacancies are found to be unevenly distributed across the unit cell. Most vacancies are formed in the O (4u) and O (2s) planar positions. The O (1g) apical positions are also partly vacant. The high spin state of Co3+ ions in octahedra has been found to be realized. This conclusion obtained from neutron diffraction data is consistent with the results of X-ray absorption spectroscopy.

Solid solutions CaLa2-xEu x Ge3O10 (x = 0.0–0.6, Δx = 0.1) have been synthesized for the first time. The compounds are isostructural to CaLa2Ge3O10, they crystallize in the monoclinic system, space group P21/c, Z = 4. The low-temperature X-ray diffraction studies have revealed the strain anisotropy of germanate CaLa2Ge3O10 crystal lattice in the temperature range 80–298 K, and the linear thermal expansion coefficients have been calculated. The optical properties of the activated phases have been studied, and the influence of the dopant concentration and the excitation wavelength on the luminescence characteristics of the synthesized compounds has been established.

Samples of fuel claddings after their operation life in the BN-600 reactor have been investigated. They were irradiated with fast neutrons with a damage dose from the range 1.5-81.4 dpa and at temperatures from 643 to 798 K. Using the FullProf program analysis, data on the microstructure, texture, and microdeformations were gained. From the anisotropic broadening of reflections estimated by the Williamson-Hall method, the density of dislocations and their type were calculated. A conclusion is made on a significant impact of the irradiation temperature on the dislocation density. It is shown that neutron diffraction is an attractive way of investigation of microstructure of massive samples subjected to such high irradiation doses without leading the staff into any radiation danger. Published by Elsevier B.V.

Aluminium and gallium hydroxide diformates have been synthesized. Both compounds exhibit similar monoclinic lattice, according to the X-ray, neutron diffraction and IR spectroscopy data. Their samples possess a bright light-blue emission under UV excitation. The origin of intrinsic emission is elucidated by means of DFT calculations.

Structural and microstructural changes that arise in the course of the heat treatment of Cr–Ni–Mo austenitic stainless steels with different concentrations of titanium and phosphorus have been studied. It has been found that the alloying with phosphorus decreases the lattice parameter of these steels. The phosphorus contribution to this effect is 0.015 ± 0.002 Å/at %. Aging at a temperature of 670 K for about 20 h leads to the precipitation of dispersed needle-like particles, which are most likely to be iron phosphides. In the temperature range of 700–800 K, in austenitic steels, the atomic separation of the solid solution occurs, the intensity of which decreases upon alloying with titanium or phosphorus at concentrations of 1.0 and 0.1 wt %, respectively. At higher temperatures (about 950 K), the formed precipitates of the Ni3Ti (γ') phase increase in size to 7–10 nm.

AbstractSolid solutions CaLa_2- x Eu_ x Ge_3O_10 ( x = 0.0–0.6, Δ x = 0.1) have been synthesized for the first time. The compounds are isostructural to CaLa_2Ge_3O_10, they crystallize in the monoclinic system, space group P 2_1/ c , Z = 4. The low-temperature X-ray diffraction studies have revealed the strain anisotropy of germanate CaLa_2Ge_3O_10 crystal lattice in the temperature range 80–298 K, and the linear thermal expansion coefficients have been calculated. The optical properties of the activated phases have been studied, and the influence of the dopant concentration and the excitation wavelength on the luminescence characteristics of the synthesized compounds has been established.

The applicability of the method of high-resolution neutron diffraction for determining defects (dislocations) in the bulk of a material is shown based on the example of a standard sample of deformed copper. The structural state of several samples of fuel-element claddings made of cold-worked steel 16Cr–15Ni–2Mo–2Mn–Ti–V–B (grade ChS68-ID) used in the BN-600 reactor, which were prepared by two producers, i.e., at the PJSC Mashinostroitel’nyi Zavod (MSZ) and at the PJSC Pervoural’sk Novotrubnyi Zavod (PNTZ), have been investigated. The conclusion has been drawn that the claddings have a texture in which the crystallographic planes of grains are oriented along the axis of the shells. It has been shown that the main defects in these claddings are edge dislocations; their density has been determined.

Analysis of correlation between structural features and rubidium ion conductivity is performed for RbFeO2 polymorphs in a wide temperature range of 296–843 K. To explore the migration maps of Rb+ cations, we used neutron diffraction data for low- and high-temperature RbFeO2 polymorphs and natural tiling concept implemented in the TOPOS software. Five independent elementary channels for the Rb+ cation migration have been revealed whose cross- sections were found to be essentially different in the low-temperature form, indicating a high anisotropy of the cation conductivity. During the transition to the cubic high-temperature phase all five channels become equivalent with sharply increased cross-sections, which accounts for the increase of cations mobility and gives rise to the three-dimensional character of conductivity.

The structure of dry and hydrated perovskite La0.9Sr0.1ScO3−δ has been studied by means of X-ray and neutron powder diffraction methods. Preferable positions for oxygen vacancies and deuterons in the oxide have been determined. Thermodynamics of water vapour uptake and transport phenomena have been experimentally investigated at pH2O=0.24atm and pO2=0.18atm in the temperature range from 300 to 950°С. The enthalpy and entropy of hydration reaction have been calculated. The oxidation enthalpy for two possible mechanisms of hole transfer (band conduction and small polaron hopping) have been estimated. The electrical conductivity has been investigated by means of impedance spectroscopy measurements in the temperature range from 500 to 900°С and at the oxygen partial pressures of 10−20atm<pO2<0.21atm. The oxygen surface exchange and diffusion coefficients have been obtained by means of the isotope exchange method with gas phase equilibration in the temperature range of 600–900°С and at the oxygen partial pressure 0.01atm. The dependences of the transference numbers of protons, oxygen ions and holes on external conditions have been determined. The La0.9Sr0.1ScO3−δ oxide was found to be a pure protonic conductor at temperatures below 600°С under reducing conditions.

Crystal structure and magnetic and thermomagnetic properties of the (TmxPr1-x)(2)Fe-17 system have been studied. The alloys with x = 0-0.4 and x = 0.8-1 crystallize into a rhombohedral structure of the Th2Zn17-type and into a hexagonal structure of the Th2Ni17-type, respectively. Both these structures coexist in the concentration range x = 0.5-0.75. The compounds with 0 < x < 0.6 are ferrimagnets, while in the compounds with x = 0.6-1, an additional high-temperature helimagnetic state appears. The lattice parameters, spontaneous magnetization, and the peak entropy change -Delta S-M of the (TmxPr1-x)(2)Fe-17 system decrease with increasing Tm content. The temperatures of helimagnetic ordering and ferrimagnet-to-helimagnet transition decrease non-monotonically as Tm content increases, with the minimum values being for the composition with x = 0.8. Microdeformations in the alloys with x = 0.5-0.9 have been detected by means of neutron diffraction. (C) 2017 Elsevier B.V. All rights reserved.

Методом высокотемпературной нейтронографии исследована кристаллическая структура галлата рубидия RbGaO2 в интервале температур 300-853 K. Методом компьютерного моделирования с использованием программы TOPOS определены каналы, доступные для движения катионов рубидия в низко- и высокотемпературной формах RbGaO2. Установлена корреляция между радиусом сечения каналов миграции и рубидий-катионной проводимостью. Работа выполнена с использованием УНУ "НМК ИФМ" в рамках государственного задания ФАНО России (тема "Поток", N 01201463334).

The crystal structure of rubidium gallate RbGaO2 in the temperature range of 300–853 K has been investigated using high-temperature neutron diffraction. The channels available for the motion of rubidium cations in the low-temperature and high-temperature modifications of RbGaO2 have been determined using the computer simulation with the TOPOS program. A correlation between the radius of the migration channel cross section and the rubidium cation conductivity has been established.

Nickel specimens subjected to fast-neutron irradiation followed by annealings have been examined using neutron and X-ray diffraction. The type of structural defects, which result from the fast-neutron irradiation of nickel crystals, has been first identified using neutron diffraction and the experimental dependence of the lattice parameter on the concentration of interstitial defects has been determined. It is shown that the changes in the lattice parameters due to both irradiation and annealings are primary related to the variations in the concentration of interstitial atoms in the lattice.

Ba7Li1.75Mn3.5O15.75 is a new hexagonal perovskite whose crystal structure has elements typical for the layered hexagonal perovskites and quasi-one-dimensional oxides, hence representing a new polytype. It has been synthesized via a solid-state microwave route. The crystal structure was solved using a combination of X-ray and neutron diffraction data, which show that Ba7Li1.75Mn3.5O15.75 crystallizes in a hexagonal unit cell with parameters a = 5.66274(2) Å and c = 16.7467(1) Å (V = 465.063(4) Å(3)), with one formula unit, and can be described as columns of face-shared octahedra occupied by Mn(4+) and Li(+) cations and vacancies along the c axis separated in the ab plane by barium atoms. Every sixth layer, the coordination of Mn(5+) and Li(+) changes to tetrahedral. Additional local ordering of manganese and lithium atoms among cationic sites leading to the formation of a rhombohedral supercell has been observed by scanning transmission electron microscopy.

A new hexagonal perovskite, Ba7Li1.75Mn3.5O15.75, has been synthesised using microwave-assisted solid-state synthesis. Its crystal structure has elements typical for the layered hexagonal perovskites and quasi-one-dimensional oxides, hence representing a new polytype. Structural solution based on simultaneous refinement of X-ray and neutron diffraction data shows that Ba7Li1.75Mn3.5O15.75 crystallizes in a hexagonal unit cell with parameters a = 5.66274(2) A and = 16.7467(1) A (V = 465.063(4) a(3)). Columns of faceshared octahedra occupied by Mn4+, Li+ cations and vacancies along the. axis are separated in the ab plane by barium atoms, so that every sixth layer, the coordination of Mn5+ and Li+ changes to tetrahedral. Separation of Mn4+ and Mn5+ cations in two distinct structural positions makes the structure unique. A scanning transmission electron microscopy study revealed the formation of a rhombohedrally centered supercell, which might be attributed to the ordering of manganese and lithium atoms among cationic sites.