Substitution solid solutions CuCr1-xZrxSe2, x = 0-0.2 have been synthesized for the first time. The crystal structure and phase equilibria of these samples were studied in the temperature range of 100-700 degrees C. It was found that the delafossite-like crystal structure is stable in the whole temperature and concentration range studied. It was found that parasitic phases, binary copper and chromium selenides and spinels CuCr2Se4 and Cu (Cr1-xZrx)2Se4, are formed during the synthesis. Their appearance is because doping with zirconium does not affect the crystal structure. Instead, it affects the thermodynamic stability of the CuCr1-xZrxSe2 solid solution with a delafossite-like structure.

Analysis of the first-order transition between D03 and two close-packed phases (L12, D019) in Fe3Ga-type alloy (26.9 %Ga), is carried out at different cooling rates from the range of equilibrium D019 phase and at different cooling rates from the range of equilibrium A2 phase. The structure was controlled by neutron diffraction, SEMEBSD and additionally characterized using VSM and ATP tests. The obtained results clarify kinetics of D019 phase growth and transition to low temperature equilibrium L12 phase. We demonstrated that D019 phase is ferromagnetic at room temperature with very low saturation magnetostriction.

The evolution of the structural phases of the Fe-42.4 at% Ga alloy was studied using neutron diffraction performed with high-intensity continuous scanning in a wide temperature range. The sequence of occurrence of structural states both during heating and subsequent cooling is reported. The structural phases Fe13Ga13, Fe13Ga9, alpha-Fe6Ga5, D03, L12, A2 are present in the alloy and they disappear upon heating above 800 degrees C into the partially ordered B2/A2 phase. The high-temperature Fe13Ga13 intermetallic compound exists in two temperature ranges: 25-580 degrees & Scy; and 770-800 degrees & Scy; during heating and precipitates again during cooling. The persistence of the phase upon cooling down to room temperature is inconsistent with the phase diagram, indicating that the alloy remains in a metastable state after the heating and subsequent cooling. The D03, alpha-Fe6Ga5 and L12 phases are formed during cooling.

Prussian white is the promising cathode material for rechargeable sodium ion batteries. Here we study phase transitions in commercial Prussian White powder with particle size up to 10 μm, which was chemically enriched with sodium, and synthesized sodium-enriched Prussian White with particle size of 1 μm. X-ray diffraction was used to track structural changes during heating up to 250°C. Both powders were found to undergo the transformation of initial rhombohedral phase to dehydrated rhombohedral phase through a formation of cubic phase. Smaller particle size of the synthesized powder leads to more effective dehydration, which decreases temperatures of all phase transitions by ≈10°C compared to commercial Na-enriched Prussian White.

The high-resolution Fourier diffractometer (HRFD) has been in routine operation since 1994 at the long-pulse neutron source, the IBR-2 reactor, in Dubna. Its fast Fourier chopper provides probably the best compromise between very high resolution in reciprocal space (Δd/d ≈ 0.001) and the intensity. For further improving intensity of TOF-diffraction pattern, a wide-aperture ring backscattering detector (BSD) has been developed on the basis of ZnS(Ag)/6LiF scintillator. BSD is designed in the form of 6 concentric rings, each of which is subdivided into 12 identical parts. The main parameters of the detector are the following: range of scattering angles is 2θ = (133 - 175) degrees, covered solid angle is Ωd ≈ 2.0 sr, average percentage absorption efficiency gets closer to 85%, geometrical contribution to resolution function does not exceed Δd/d = 0.0005. In the report the concept of the detector is described and its data acquisition system is presented. The start of operation of the detector at the HRFD is scheduled for 2024.

Prussian White (PW) is a promising cathode material for sodium-ion batteries. PW exhibits advantages such as high specific capacity, ease of synthesis, and low cost. However, the presence of interstitial and coordinated water in PW materials significantly influences their electrochemical properties. In this work, a dehydration of the commercial PW powder and an impact of the preheating of the PW electrodes on their structural and electrochemical behavior have been examined using in situ/operando neutron and X-ray diffraction, along with complex TG-IR and FTIR techniques. The dehydration of the PW powder under the vacuum annealing conditions occurs mainly between 100 and 150 C-degrees. At temperatures above 180 C-degrees, a decomposition of the PW powder is detected. Preheating the electrode at 180 C-degrees promotes the formation of a larger fraction of dehydrated rhombohedral phase, resulting in higher capacity compared to electrodes without preheating and preheated at 140 degrees C. Carbon content has been shown to be an important factor for stable electrode cycling. Capacity values of similar to 100 mAh g(-1) and 83 mAh g(-1) at 5 C and 10 C-degrees cycling rates, respectively, are achieved when using 15 wt% content of carbon additive for the electrode preparation. Structural aspects of the degradation of PW electrodes during cycling are discussed.

Currently, the dominant model for the formation of enhanced magnetostriction of Fe-Ga alloys is based on the assumption of the presence of microscopic inclusions with a tetragonal L60 structure in the cubic matrix of the alloy. However, no evidence for the presence of this phase in the bulk of the alloys in amounts sufficient to have a noticeable effect on the magnitude of magnetostriction has been obtained so far. To test this hypothesis, a detailed scanning of the reciprocal space of Fe81Ga19Tb0.1 and Fe73Ga27 single crystals was carried out at ESRF at high photon flux stations. In particular, it was possible to reliably record superstructure diffraction peaks, the intensity of which was at a level of 2 x 10-6 from the intensity of the fundamental peaks. Nevertheless, neither the presence of superstructure diffraction peaks obviously belonging to the L60 phase nor the tetragonal splitting of the fundamental diffraction peaks into components, which could indicate the presence of this phase in the samples, was detected. Similar results were obtained using complementary methods (electron and neutron diffraction). Based on the performed analysis of the background level in the places of the expected positions of superstructure peaks of the L60 phase, it was found that the volume fraction of this phase in the Fe81Ga19Tb0.1 alloy cannot exceed 0.2%. The presence of a previously discovered X phase with hexagonal or orthorhombic symmetry in a crystal with 27 at. % Ga was confirmed.

New data on phase states and structural phase transitions in alloys Fe73Ga27 doped with Dy, Er, Tb, and Yb in an amount of about 0.5 at

Abstract—New data on the phase compositions and structural transformations in a number of Fe81Ga19 alloys doped with trace amounts (≤0.2 at

Analysis of the first-order transition between D03 and two close-packed phases (L12, D019) in Fe3Ga-type alloy (26.9%Ga), is carried out at different cooling rates from the range of equilibrium D019 phase and at different cooling rates from the range of equilibrium A2 phase. The structure was controlled by neutron diffraction, SEM-EBSD and additionally characterized using VSM and ATP tests. The obtained results clarify kinetics of D019 phase growth and transition to low temperature equilibrium L12 phase. We demonstrated that D019 phase is ferromagnetic at room temperature with very low saturation magnetostriction.

In situ neutron diffraction and internal friction were combined for the comparative analysis of structural and functional properties of Fe-26Al alloy. Three different alloy states were studied: after rapid solidifica-tion in graphite mold, after annealing at 900 degrees C (0.5 h) and water quenching, after annealing at 450 degrees C (24 h) and slow cooling. Structural phase states and microstructure types were determined. The obtained results make it possible establishing the relationship between the thermal treatments, microstructure, phase transformations on the one hand and anelastic (internal friction) properties on the other.(c) 2022 Elsevier B.V. All rights reserved.

The effect of various cooling regimes on the evolution of the crystal structure of entropy- stabilized oxides (MgNiCoCuZn)O has been studied using a high-resolution time-of-flight neutron Fourier diffractometer. It has been established that cooling in a furnace at a rate of 1, 2, and 5 K/min leads not only to the segragation of a part of copper oxide into a separate phase, but also to nanostructuring of both the main matrix and CuO. The characteristic sizes of the formed nanoparticles are determined. It is shown that the expected rhombohedral or tetragonal distortions due to the possible Jahn-Teller effect are not observed in these samples.

The evolution in phase composition of as-cast Fe-(31-35) at% Ga alloys during continuous heating up to 850 degrees C with subsequent cooling was studied. Based on the results obtained by neutron diffraction, con-clusions were drawn about clearly distinguishable stages of phase formation during heating and cooling of metastable high-gallium alloys. Upon heating, the phase composition of studied alloys was found to change in a similar way, namely: BCC + Fe13Ga9 (absent in Fe-31.1 at% Ga) -> BCC+ Fe13Ga9 + L12 -> BCC + L12 + alpha- Fe6Ga5 -> B2 + alpha-Fe6Ga5 -> B2. Upon cooling, the following sequence of phase states was realized in Fe-32.9Ga and Fe-34.4 at% Ga alloys: B2 -> B2 + alpha-Fe6Ga5 -> D03 + L12 + alpha-Fe6Ga5. Fe-31.1 at% Ga alloy was found to be characterized by the sequence: B2 -> B2 + L12 -> D03 + L12 + Fe13Ga9. (c) 2022 Elsevier B.V. All rights reserved.

Эволюция структурных фаз и микроструктурного литого состояния составов Fe100-(x+y)GaxAly в диапазоне 17≤(x+y)≤39 at.% изучена в нейтронных дифракционных экспериментах, выполненных с высоким разрешением и в режиме непрерывного сканирования по температуре при нагреве до ~ 900oС и последующем охлаждении. Установлено, что структуры литых состояний тройных сплавов в изученном диапазоне содержания Ga и Al в основных чертах повторяют структуру двойных составов Fe100-xGax до x~ 30 и Fe100-yAly до y~ 50. А именно, в них наблюдаются только кубические фазы (А2, D03 и B2), а гексагональные (A3, D019) и моноклинные (типа Fe13Ga9 или α-Fe6Ga5) фазы, характерные для системы Fe-Ga, отсутствуют. Расширение диапазона образования кубических фаз, образующихся на основе ОЦК-ячейки, в тройных сплавах по сравнению с Fe100-xGax, свидетельствует о роли Al в стабилизации этих структур. Ключевые слова: сплавы Fe-Ga, Fe-Al, Fe-Ga-Al, структурные фазовые переходы, дифракция нейтронов, магнитострикция.

Evolution of structural phases and microstructural cast state of Fe 100-(x+y) Ga x Al y compositions in the range of 17≤(x+y)≤39 at.% was studied in neutron diffraction experiments performed with high resolution and in continuous temperature scanning mode when heated to ~ 900 o C and subsequent cooling. It is established that the structures of the cast states of triple alloys in the studied range of Ga and Al content basically repeat the structure of the double compositions Fe 100-x Ga x up to x~ 30 and Fe 100-y Al y up to y~ 50. Namely, only cubic phases (A2, D0 3 and B2) are observed in them, and hexagonal (A3, D0 19 ) and monoclinic (such as Fe 13 Ga 9 or α-Fe 6 Ga 5 ) there are no phases characteristic of the Fe-Ga system. The expansion of the range of formation of cubic phases formed on the basis of the BCC cell in ternary alloys in comparison with Fe 100-x Ga x indicates the role of Al in the stabilization of these structures. Keywords: alloys Fe-Ga, Fe-Al, Fe-Ga-Al, structural phase transitions, neutron diffraction, magnetostriction.

The thermoelastic martensitic transformation in the polycrystalline Ti29.7Ni50.3Hf10Zr10 alloy was studied using high-resolution and in situ neutron diffraction in the temperature range of 25-250 degrees C. The thermal expansion tensors of the B19' martensite and austenite were determined. B19' martensite is characterized by a strong anisotropy of the thermal expansion coefficients. The analysis of the diffraction peak integrated intensities suggests that nearly 10% of austenite, which is partly disordered, does not take part in martensitic transformation. The volume effect of the transformation in the Ti29.7Ni50.3Hf10Zr10 alloy was 0.79%. The simultaneous addition of Hf and Zr atoms into the TiNi matrix leads to the deterioration of the crystallographic compatibility between martensite and austenite, which may be responsible for the large thermal hysteresis and volume changes upon transformation. (C) 2021 Elsevier B.V. All rights reserved.

In our work, we synthesized a series of P2-Na0.7MnO2 (NMO) and P2-Na0.7Ni0.33Mn0.67O2 (NNMO) cathode materials by sintering from precursor powders at a temperature of 900°C in a stationary or in a flowing air atmosphere. By means of X-ray diffraction analysis it was shown that the material resulting composition strongly depends on the annealing conditions. During the synthesis in a stationary atmosphere, P2-contained samples of mixed sodium–nickel–cobalt oxide were obtained. At the same time, the structural disordering observed in the NMO material disappeared after the NMO coating with an admixture of sodium-nickel oxide (NNMO). The NNMO samples demonstrated a higher discharge capacity of 149 mA h g–1 compared to 123 mA h g–1 NMO. However, the coating effect was not able to prevent a rapid drop in capacity during cycling.

The evolution of structural phases and the morphology of the microstructure of several Fe-xAl and Fe-xGa compositions were studied by neutron diffraction with high Delta d/d resolution and with high-intensity continuous scanning in a wide temperature range. It was found that the formation of an ordered structure upon a change in the Al or Ga content or during a phase transition upon a change in temperature leads to a decrease in the unit-cell parameter with a "jump" of the order of Delta a/a similar to 0.001. A specific microstructure in the form of mesoscopic clusters (L similar to 200-1000 A) with an ordered atomic structure dispersedly incorporated into a disordered or less ordered matrix can be formed in the ranges of 23 at% < x < 33 at% for Fe-xAl and 19 at% < x < 24 at% for Fe-xGa. Independent determination of the unit-cell parameters of the matrix and clusters showed their coherence, which is manifested in their coincidence or proximity with a high degree of accuracy (Delta a/a <= 0.0001). This type of phase separation (matrix + clusters) has a completely different nature with an incoherent phase coexisting in the outer or thin layers, which leads to lattice parameters difference at the level of Delta a/a similar to 0.001. (C) 2021 Elsevier B.V. All rights reserved.

Single crystal synchrotron diffraction was used for detailed analysis of ordering effects in alloys with a nominal composition of Fe80.5Ga19.5 and Fe73.1Ga26.9. The first composition manifests a disordered average A2 structure with local fluctuations resembling a D0(3) ordering motif in the lengthscales of similar to 50 angstrom. In Fe73.1Ga26.9 alloy ordered over a long range, a D0(3) matrix coexists with similar to 100 angstrom inclusions of a new ordered phase, presumably hexagonal with lattice parameters a approximate to root 8a(0) and c approximate to root 12a(0), where a(0) = 2.87 angstrom is the unit cell dimension of body-centered cubic Fe.