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Advancements and utilization of magnetic refrigeration technology hinge on the ongoing enhancement and optimization of magnetic refrigeration material properties. Nevertheless, the intricacy of the magnetocaloric effect (MCE) mechanism has emerged as a bottleneck, constraining the progress and refinement of magnetic refrigeration materials. In this study, a classic magnetic system is chosen to investigate the mechanism of MCE across four different scales–macroscopic magnetism, micrometer‐scale magnetic domains, atomic magnetic moments, and electronic structure. It simultaneously exhibits two inverse MCEs and one direct MCE, with a working temperature span as wide as 125 K (most are <50 K) for the direct MCE. The measurements of the vibrating sample magnetometer, in situ Lorentz electron microscopy and variable‐temperature neutron powder diffraction directly reveal that the complex magnetic entropy changes arise from the magnetic domain wall pinning, the instability of Ho magnetic moments, and the spin rotation. First‐principles calculations elucidate the crucial role of strong hybridization between localized Ho and itinerant Co electrons in the spin reorientation of HoCo4Al. This study contributes significantly to comprehending the induction mechanism of the MCE and holds vital reference value for exploring new magnetic refrigeration materials and enhancing MCE performance. [ABSTRACT FROM AUTHOR]

A neutron time‐of‐flight (TOF) powder diffractometer with a continuous wide‐angle array of detectors can be electronically focused to make a single pseudo‐constant wavelength diffraction pattern, thus facilitating angle‐dependent intensity corrections. The resulting powder diffraction peak profiles are affected by the neutron source emission profile and resemble the function currently used for TOF diffraction. [ABSTRACT FROM AUTHOR]

Thiophosgene is one of the principal C=S building blocks in synthetic chemistry. At room temperature, thiophosgene is a red liquid. While its properties in the liquid and gaseous states are well known, a comprehensive characterization of thiophosgene in its solid state is presented here. Differential scanning calorimetry shows that thiophosgene forms a supercooled melt before rapidly crystallizing. Its melting point is 231.85 K (−41.3 °C). At 80 K, thiophosgene crystallizes in space group P63/m [No. 174, a = b = 5.9645 (2), c = 6.2835 (3) Å, V = 193.59 (2) Å3]. The molecule shows a distinct rotational disorder: all S and Cl positions are of mixed occupancy and the disorder does not resolve at temperatures as low as 10 K, as was shown by neutron powder diffraction. Infrared, Raman and inelastic neutron scattering spectra were collected and assigned with the aid of quantum chemical calculations. A larger ordered structural model allowed for better agreement between the measured and calculated spectra, further indicating that disorder is an inherent feature of solid‐state thiophosgene. [ABSTRACT FROM AUTHOR]

CaAl12O19, which can incorporate Ti as both Ti3+ and Ti4+ (charge coupled substitution with Mg2+), is one of the first minerals to condense from a gas of solar composition and is used as a ceramic. It is variously known as hibonite, calcium hexaluminate (CaO.6Al2O3), and CA6. The lattice parameters and unit cell volumes of Ti-substituted hibonite (P63/mmc) with the formulae CaAl11.8Ti3+0.2O19 and CaAl9.8Ti3+0.54Mg0.83Ti4+0.83O19 were determined as a function of temperature from ~ 10 to 275 K by neutron powder diffraction. The thermal expansion is highly anisotropic with the expansion in c a factor of ~ 5 greater than that in a. The change in a is approximately equal for the two compounds whereas the change in c is almost 50% larger for CaAl11.8Ti3+0.2O19. CaAl11.8Ti3+0.2O19 also exhibits negative thermal expansion between 10 and 70 K. The change in unit cell volume with temperature of both compositions is well described by a two term Einstein expression. The large change in c is consistent with substitution of Ti onto the M2 and M4 sites of the R-block structural unit. [ABSTRACT FROM AUTHOR]

CaAl12O19, which can incorporate Ti as both Ti3+ and Ti4+ (charge coupled substitution with Mg2+), is one of the first minerals to condense from a gas of solar composition and is used as a ceramic. It is variously known as hibonite, calcium hexaluminate (CaO.6Al2O3), and CA6. The lattice parameters and unit cell volumes of Ti-substituted hibonite (P63/mmc) with the formulae CaAl11.8Ti3+0.2O19 and CaAl9.8Ti3+0.54Mg0.83Ti4+0.83O19 were determined as a function of temperature from ~ 10 to 275 K by neutron powder diffraction. The thermal expansion is highly anisotropic with the expansion in c a factor of ~ 5 greater than that in a. The change in a is approximately equal for the two compounds whereas the change in c is almost 50% larger for CaAl11.8Ti3+0.2O19. CaAl11.8Ti3+0.2O19 also exhibits negative thermal expansion between 10 and 70 K. The change in unit cell volume with temperature of both compositions is well described by a two term Einstein expression. The large change in c is consistent with substitution of Ti onto the M2 and M4 sites of the R-block structural unit. [ABSTRACT FROM AUTHOR]

In this work, a comprehensive analysis of the structural and magnetic properties of the M-type hexaferrite (BaFe 12 O 19 and SrFe 12 O 19) was conducted using the chemical co-precipitation approach. The analytical techniques employed include powder X-ray diffraction, Transmission Electron Microscopy, Fourier Transform Infrared Spectroscopy, and Thermogravimetric Analysis. Powder Neutron Diffraction was utilized to analyse the magnetic ordering and crystal structure. A hexagonal crystal structure with space group P 6 3 / mmc was obtained from to structural analysis. Additionally, the investigation encompassed an assessment of the maximum energy product (BH) max and magnetic properties utilizing Vibrating Sample Magnetometry across all synthesized materials. Magnetic investigations of the studied materials showed several interesting characteristics: SrM showed a maximum saturation magnetization of 49.67 emu/g and a maximum coercivity of 4874.55 Oe. Remarkably, SrFe 12 O 19 showed twice as much saturation magnetization and remnant magnetization than BaFe 12 O 19 , suggesting more robust and effective magnetic parameters. The overarching objective of this study is to discern the optimal hexaferrite material, evaluating magnetism, coercivity, thermal stability, and energy output through a systematic exploration of crystal structure, magnetic properties, thermal behaviour, manufacturing methodologies, and microstructure. This research endeavour not only contributes crucial insights into the potential applications of both BaM and SrM but also considers their environmental implications. The study further provides valuable recommendations for selecting the most efficacious material for specific permanent magnet applications, thereby contributing to the advancement on the field of magnetic engineering. The culmination of this work is poised to facilitate informed decision-making and technological progress in the realm of hexaferrite materials with a deliberate consideration of their environmental impact. [ABSTRACT FROM AUTHOR]

Co-doped NiMnSn Heusler-type metamagnetic shape memory alloys (MMSMAs) are promising materials for the next-generation solid-state refrigeration systems due to their excellent magnetocaloric performance around the martensitic transformation, which is easily tuneable by slight changes in the alloy composition. An improvement in the thermal efficiency of active magnetic regenerator devices, a key element in magnetocaloric cooling systems, arises by obtaining powdered magnetocaloric alloys that meet technical requirements for their implementation as a feedstock material in the additive manufacturing of 3D-printed heat exchangers. In the present work, powders of Mn-rich NiCoMnSn Heusler-type MMSMAs were obtained from their ribbon form avoiding or minimizing residual stresses, the number of defects and disorder in the crystal lattice and microstructure. Since atomic order and crystallographic structure are crucial in the transformation and magnetic properties of these alloys, a complementary structural analysis of the powders after different heat treatments was performed by powder neutron diffraction. The results show that the cubic austenitic phase of the non-heat-treated melt-spun powder exhibits a highly stressed structure, which leads to an incomplete martensitic transformation and, therefore, to the coexistence of martensitic and austenitic phases at low temperatures. The magnetic structure of the austenite phase was also determined by neutron powder diffraction, obtaining a ferromagnetic coupling between 4a and 4b Wyckoff positions in the samples analysed. It was found that a heat treatment facilitates the martensitic transformation and enables the formation of a pure martensitic phase.The observed changes in the magnetocaloric performance of the powders have been understood in terms of the differently stressed structures and their impact on the martensitic transformation. A fully completed structural transformation leads to a significant increase of the magnetisation change across the martensitic transformation and, consequently, to high values of both a magnetic field induced isothermal entropy change and refrigeration capacity.

Magnetic materials with non-collinear spin orderings provide an outstanding platform to probe spintronic phenomena owing to their strong spin-orbit coupling (SOC) and unique Berry phase. It is thus important to obtain a non-collinear antiferromagnetic (AFM) phase at room temperature (RT). Significantly, the discovery of novel materials with nearly zero thermal expansion (ZTE) property near RT is required and pursued for avoiding thermal stress and fracture in spintronic devices. Herein, the doping of Sn (Ge) at the Ag site in the triangular lattice Mn3Ag1−xSn(Ge)xN compounds increases effectively the Néel point and makes the interesting non-collinear Γ5g AFM phase exist above RT. The magnetic phase diagrams with Γ5g phase up to 498 K were built by the combined analysis of neutron powder diffraction (NPD), magnetic measurements, electronic transport, and differential scanning calorimetry (DSC). The thermal expansion behaviors of Mn3Ag1−xSn(Ge)xN were modulated, and the nearly ZTE above RT was achieved in Mn3Ag0.5Ge0.5N within Γ5g AFM ordering. Our findings offer an effective way to tailor the non-collinear AFM ordering and correlated thermal expansion behavior for potential use in the emerging field of thermal stress-free magnetic chip materials.

Crystal structure features of two samples of layered honeycomb oxides of stoichiometric composition Li2Ni2TeO6, synthesized from Na2Ni2TeO6 and K2Ni2TeO6 precursors, are determined via neutron powder diffraction at 35 K, slightly above the Néel temperature. They have a similar P2-type crystal structure with hexagonal space group P63/mcm, but a considerable difference in the distances between layers. Both Li2Ni2TeO6 samples crystallize in orthorhombic space group Cmca, with minor differences in the unit cell parameters. Li2Ni2TeO6 from the potassium precursor is single-phase, while 16 wt % of an additional phase with the same Li2Ni2TeO6 stoichiometry but more deformed and having monoclinic distortions described by the C2/m space group is found in the compound from the sodium precursor. [ABSTRACT FROM AUTHOR]

This article focuses on the Na2O-Ga2O3-TiO2 system, which is barely explored in the study of transparent conductive oxides (TCOs). NaxGa4+xTin−4−xO2n−2 (n = 5, 6, and 7 and x ≈ 0.7–0.8) materials were characterized using neutron powder diffraction and aberration-corrected scanning transmission electron microscopy. Activation energy, as a function of different structures depending on tunnel size, shows a significant improvement in Na+ ion conduction from hexagonal to octagonal tunnels. New insights into the relationship between the crystal structure and the transport properties of TCOs, which are crucial for the design and development of new optoelectronic devices, are provided. [ABSTRACT FROM AUTHOR]

Complex perovskite La2(Al1/2MgTa1/2)O6 (LAMT) crystallizes in a monoclinic unit cell with space group P21/n at room temperature. Its B-site cations are ordered in a rock-salt-type arrangement. Previously, the full occupancy of Mg on the 2c-Wyckoff position was deduced from powder X-ray diffraction (PXRD). However, conventional X-rays could not properly resolve the mixed occupation on the B-site, since there is little scattering contrast between the neighbouring elements Mg and Al of the periodic table. Hence, complementary neutron diffraction studies were carried out to verify the exact B-site cation ordering in the unit cell. In this specific configuration of the B-cations, with its occupancy ratio and the presence of a heavy element Ta as well as neighbouring elements Mg and Al, only the strategy of a combined Rietveld analysis using both the X-ray and neutron diffraction data simultaneously succeeded in elucidating an accurate B-site cation ordering in this complex perovskite system. A full occupancy of Mg on the 2c-Wyckoff position and each a half occupancy of Al and Ta on the 2d-Wyckoff position could be resolved for the rock-salt-type ordering of the B-site cations in the monoclinic unit cell of LAMT.

The recovery and utilization of carbon dioxide (CO2) is the key to achieve the targets of peak carbon dioxide emissions and carbon neutrality. The Na‐CO2 battery made with cheap alkali metal sodium and greenhouse gas CO2 is an effective strategy to consume CO2 and store clean renewable energy. However, the liquid electrolyte volatilization in the open battery system and inevitable dendrite growth restrict the application of Na‐CO2 batteries. In this work, magnesium‐doped Na3Zr2Si2PO12 (NZSP) was studied as a solid electrolyte for solid‐state Na‐CO2 batteries. The ionic conductivity of Na3.2Zr1.9Mg0.1Si2PO12 reaches 1.16 mS cm−1 at room temperature by replacing Zr ions in Na3Zr2Si2PO12 with Mg ions, and the structural changes are analyzed by neutron powder diffraction. The composite electrolyte consisting of highly conductive Na3.2Zr1.9Mg0.1Si2PO12 and high processability poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) is utilized for the first time to assemble a solid‐state Na‐CO2 battery. The cell shows a full discharge capacity of 7720 mAh g−1 at 200 mA g−1. The middle gap voltage is lower than 2 V after 120 cycles at 200 mA g−1 and at a cut‐off capacity of 500 mAh g−1. This work demonstrates a promising strategy to design high‐performance solid‐state Na‐CO2 batteries. [ABSTRACT FROM AUTHOR]

We report the high-temperature magnetic ordering and the observation of linear negative magnetocapacitance mediated by a low-temperature magnetic phase crossover in the compound LiFe _2 SbO _6 . The combined observations of the absence of a second harmonic generation (SHG) signal, and Rietveld refinements of x-ray and neutron powder diffraction (NPD) patterns of the sample confirm that LiFe _2 SbO _6 crystalizes in a centrosymmetric Pnnm structure. The DC magnetization measurements reveal that an antiferromagnetic ordering sets in at high temperature ( T _N = 850). The magnetic anomaly in the DC magnetization at a lower temperature T = 13 K, is corroborated by AC susceptibility and the specific heat measurements. In association with this magnetic phase crossover, a linear negative magnetocapacitance was observed below this temperature. Further, the neutron powder diffraction study reveals a collinear antiferromagnetic ordering with a wavevector k = (0, 0, 0).

Complex perovskite La2(Al1/2MgTa1/2)O6 (LAMT) crystallizes in a monoclinic unit cell with space group P21/n at room temperature. Its B-site cations are ordered in a rock-salt-type arrangement. Previously, the full occupancy of Mg on the 2c-Wyckoff position was deduced from powder X-ray diffraction (PXRD). However, conventional X-rays could not properly resolve the mixed occupation on the B-site, since there is little scattering contrast between the neighbouring elements Mg and Al of the periodic table. Hence, complementary neutron diffraction studies were carried out to verify the exact B-site cation ordering in the unit cell. In this specific configuration of the B-cations, with its occupancy ratio and the presence of a heavy element Ta as well as neighbouring elements Mg and Al, only the strategy of a combined Rietveld analysis using both the X-ray and neutron diffraction data simultaneously succeeded in elucidating an accurate B-site cation ordering in this complex perovskite system. A full occupancy of Mg on the 2c-Wyckoff position and each a half occupancy of Al and Ta on the 2d-Wyckoff position could be resolved for the rock-salt-type ordering of the B-site cations in the monoclinic unit cell of LAMT. [ABSTRACT FROM AUTHOR]

In this contribution, the novel double-perovskite La 2 Mg(Mg 1/3 Sb 2/3)O 6 has been successfully prepared by solid-state reaction method, and its structure has been determined for the first time by a combination of X-ray and neutron powder diffraction data analysis. The novel material exhibits a thermal expansion of ∼9.1 ppm/°C and a large optical band gap (4.23 eV). The complex impedance data analysis indicates that La 2 Mg(Mg 1/3 Sb 2/3)O 6 features a Debye-like behaviour, with a bulk conductivity, σ b , varying between 10-7-10-4 S ‧cm-1 within 500–900 °C temperature range, and activation energy (E a) of ∼ 1.36 eV. In addition, the microwave dielectric properties of La 2 Mg(Mg 1/3 Sb 2/3)O 6 sintered at 1625 °C display optimized quality factor (Q× f) of ∼ 28,700 GHz (f = 9.65 GHz), a dielectric constant (ε r) of ∼ 20.2 and temperature coefficient of the resonant frequency (τ f) of ∼ − 89 ppm/°C. This work widen the reduced number of A 3 + B 2 / 3 2 + B 1 / 3 5 + O 3 compounds explored so far. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, the ternary system La2O3-TiO2-Nb2O5 is studied to find new ternary phases with useful electrical properties. The solid solution La3−xTi5−3xNb10−2xO39.5−12.5x was recently identified, and this study focuses on the structural characterization of this solid solution with x = 0.04. The crystal structure, representing a new structural type, was determined from synchrotron and neutron powder diffraction data. The unit cell parameters are a = 7.332 Å, b = 7.421 Å, c = 10.673 Å, α = 84.15°, ß = 80.16°, γ = 60.37°, and space group P 1 ¯ . The titanium and niobium atoms are disordered in five different crystallographic sites coordinated octahedrally by oxygen atoms. The eight-coordinated La atoms are embedded in the octahedral framework. Ti and Nb preferentially occupy different sites, and this feature was studied using periodic density functional theory methods. Energies of possible Ti/Nb distributions were calculated and the results agree well with the site occupancies obtained by combined Rietveld refinement of synchrotron and neutron powder diffraction patterns. The geometries optimized by DFT also agree well with the structural parameters determined by diffraction. The general agreement between the theoretical calculations and the experimental data justifies the quantum chemical methods as reliable complementary tools for the structural investigation of ceramic materials. [ABSTRACT FROM AUTHOR]

Among chalcogenide thermoelectric materials, SnTe is an excellent candidate for intermediate temperature applications, in replacement of toxic PbTe. We have prepared pure polycrystalline SnTe by arc melting, and investigated the structural evolution by temperature-dependent neutron powder diffraction (NPD) from room temperature up to 973 K. In this temperature range, the sample is cubic (space group Fm-3m) and shows considerably larger displacement parameters for Te than for Sn. The structural analysis allowed the determination of the Debye model parameters and provided information on the Sn–Te chemical bonds. SEM images show a conspicuous nanostructuration in layers below 30 nm thick, which contributes to the reduction of the thermal conductivity down to 2.5 W/m·K at 800 K. The SPS treatment seems to reduce the number of Sn vacancies, thus diminishing the carrier density and increasing the Seebeck coefficient, which reaches 60 μV K−1 at 700 K, as well as the weighted mobility, almost doubled compared with that of the as-grown sample. [ABSTRACT FROM AUTHOR]

Off-stoichiometry of perovskite structural Bi0.5Na0.5TiO3 (BNT) ferroelectrics can give rise to considerable oxide-ion conductivity. The inherent structural characteristics are urgent to be resolved due to its particular sensitivity of the conduction mechanism to the nominal composition and synthesis process. Herein, a thorough study of the temperature-dependent neutron, X-ray diffraction and Raman spectrum is carried out on a series of equivalently substituted A-site deficient non-stoichiometric and pristine BNT. Phase transition and defect association are systemically investigated in these dominated rhombohedral phases at room temperature, associated with well saturated ferroelectric states. Significant structural evolution identified by Rietveld refinements and the origin of the electrical performance are clarified at elevated temperatures, focusing on the subtle distortions of ionic displacements, oxygen octahedral tilts and local chemical environments for oxygen vacancies. The ion migration ability mediated by oxygen vacancies that are not energetically favorable in BNT mainly depends on the external substitutional disorder, and is strongly affected by the dopant concentration. Together with the lone pair substitution concept, superior oxide ionic conductivity is achieved, and an alternative strategy is provided in designing BNT based oxide ion conductors.

LiNi 0.5 Mn 1.5 O 4 (LNMO) emerges as a promising spinel-type positive electrode material for lithium-ion batteries (LIBs) due to its low cost and high operating voltage (4.8 V vs. Li+/Li), attributed to the Ni4+/Ni3+/Ni2+ redox couples, which contribute to high energy density, a crucial requirement for next-generation LIBs. In this study, we investigate the influence of Mn/Ni and Li/(Mn + Ni) ratios on the phase equilibrium and electrochemical performance of LNMO positive electrode materials. A series of 18 samples were synthesized using a two-stage solid-state method with varying Mn/Ni and Li/(Mn + Ni) ratios and annealing under different atmospheres. These synthesis conditions have major impact on the composition and level of purity of LNMO phases, as well as on the nature of the impurities themselves. Mn excess significantly enhances the electrochemical performance, with superior discharge capacity, coulombic efficiency, and capacity retention for the Mn-rich sample with Li/(Mn + Ni) = 0.50. A comprehensive structural analysis combining synchrotron X-ray and neutron powder diffraction gives an in-depth characterization of these samples with a clear differentiation between the global Mn content within samples and that within the LNMO phase. • Large-scale material syntheses (300 g batches) of high-voltage spinel "LiNi0.5Mn1.5O4″ • Impact of the Mn/Ni and Li/(Mn + Ni) ratios and annealing atmosphere on the performance. • Subtle changes in composition and structure revealed by X-ray and neutron diffraction. • Sharp comprehension of high-voltage Mn-rich and Li-"poor" spinel-type materials. • Efficient materials made of sustainable elements for Lithium-ion batteries. [ABSTRACT FROM AUTHOR]

A series of low‐temperature studies on LiNi0.80Co0.15Al0.05O2 18650‐type batteries of high‐energy type with different stabilized states of fatigue is carried out using spatially resolved neutron powder diffraction, infrared/thermal imaging, and quasi‐adiabatic calorimetry. In‐plane distribution of lithium in the graphite anode and frozen electrolyte in fully charged state is determined non‐destructively with neutron diffraction and correlated to the introduced state of fatigue. An independent electrolyte characterization is performed via calorimetry studies on variously aged 18650‐type lithium‐ion batteries, where the shape of the thermodynamic signal is evolving with the state of fatigue of the cells. Analyzing the liquid electrolyte extracted/harvested from the studied cells reveals the decomposition of conducting salt to be the main driving factor for fatigue in the electrolyte degradation. [ABSTRACT FROM AUTHOR]

Iron phosphate materials have attracted a lot of attention due to their potential as cathode materials for lithium-ion rechargeable batteries. It has been shown that lithium insertion or extraction depends on the Fe mixed valence and reduction or oxidation of the Fe ions' valences. In this paper, we report a new synthesis method for the Fe3(PO3OH)4(H2O)4 mixed valence iron phosphate. In addition, we perform temperature-dependent measurements of structural and physical properties in order to obtain an understanding of electronic–structural interplay in this compound. Scanning electron microscope images show needle-like single crystals of 50 μm to 200 μm length which are stable up to approximately 200 °C, as revealed by thermogravimetric analysis. The crystal structure of Fe3(PO3OH)4(H2O)4 single crystals has been determined in the temperature range of 90 K to 470 K. A monoclinic isostructural phase transition was found at ~213 K, with unit cell volume doubling in the low temperature phase. While the local environment of the Fe2+ ions does not change significantly across the structural phase transition, small antiphase rotations occur for the Fe3+ octahedra, implying some kind of electronic order. These results are corroborated by first principle calculations within density functional theory, which also point to ordering of the electronic degrees of freedom across the transition. The structural phase transition is confirmed by specific heat measurements. Moreover, hints of 3D antiferromagnetic ordering appear below ~11 K in the magnetic susceptibility measurements. Room temperature visible light absorption is consistent with the Fe2+/Fe3+ mixed valence. [ABSTRACT FROM AUTHOR]

AgSbTe2 intermetallic compound is a promising thermoelectric material. It has also been described as necessary to obtain LAST and TAGS alloys, some of the best performing thermoelectrics of the last decades. Due to the random location of Ag and Sb atoms in the crystal structure, the electronic structure is highly influenced by the atomic ordering of these atoms and makes the accurate determination of the Ag/Sb occupancy of paramount importance. We report on the synthesis of polycrystalline AgSbTe2 by arc-melting, yielding nanostructured dense pellets. SEM images show a conspicuous layered nanostructuration, with a layer thickness of 25–30 nm. Neutron powder diffraction data show that AgSbTe2 crystalizes in the cubic Pm-3m space group, with a slight deficiency of Te, probably due to volatilization during the arc-melting process. The transport properties show some anomalies at ~600 K, which can be related to the onset temperature for atomic ordering. The average thermoelectric figure of merit remains around ~0.6 from ~550 up to ~680 K. [ABSTRACT FROM AUTHOR]

Powder X‐ray diffraction (PXRD) and neutron powder diffraction (NPD) have been used to investigate the crystal structure of CoFe2O4 nanoparticles prepared via different hydrothermal synthesis routes, with particular attention given to accurately determining the spinel inversion degrees. The study is divided into four parts. In the first part, the investigations focus on the influence of using different diffraction pattern combinations (NPD, Cu‐source PXRD and Co‐source PXRD) for the structural modelling. It is found that combining PXRD data from a Co source with NPD data offers a robust structural model. The second part of the study evaluates the reproducibility of the employed multipattern Rietveld refinement procedure using different data sets collected on the same sample, as well as on equivalently prepared samples. The refinement procedure gives reproducible results and reveals that the synthesis method is likewise reproducible since only minor differences are noted between the samples. The third part focuses on the structural consequences of (i) the employed heating rate (achieved using three different hydrothermal reactor types) and (ii) changing the cobalt salt in the precursors [aqueous salt solutions of Co(CH3COOH)2, Co(NO3)2 and CoCl2] in the synthesis. It is found that increasing the heating rate causes a change in the crystal structure (unit cell and crystallite sizes) while the Co/Fe occupancy and magnetic parameters remain similar in all cases. Also, changing the type of cobalt salt does not alter the final crystal/magnetic structure of the CoFe2O4 nanoparticles. The last part of this study is a consideration of the chemicals and parameters used in the synthesis of the different samples. All the presented samples exhibit a similar crystal and magnetic structure, with only minor deviations. It is also evident that the refinement method used played a key role in the description of the sample. [ABSTRACT FROM AUTHOR]

Zero thermal expansion (ZTE) metals have drawn considerable scientific and practical interest due to their excellent dimensional stability. However, the narrow temperature window and inherent brittleness of the ZTE compounds severely limit their processing and application. Herein, an axial ZTE alloy (Ho 2 Fe 13.8 Ni 3.2 , α l = -0.3 × 10 -6 K -1 and 110-545 K) is realized in the Ni-doped Ho 2 Fe 17 magnets, which effectively broadens the ZTE temperature window. Combining the variable-temperature neutron diffraction and magnetization measurements, we reveal that the content of Ni tailors the ferromagnetic ordering of the Fe sublattice and regulates lattice negative thermal expansion. Good compressive strength is subsequently achieved by introducing excess Fe in the axial ZTE composition, namely, the dual-phase alloy of Ho 2 Fe 13.8 Ni 3.2 -Fe 5 (α l = +0.3 × 10 -6 K -1 , 110-535 K, and 1.19 ± 0.2 GPa). Neutron diffraction and scanning electron microscopy reveal that the α phase (Fe-Ni) precipitates in the hexagonal phase matrix play a critical role in maintaining ZTE characteristics and enhancing compressive strength. The present chemical design approach may be applicable for obtaining high-performance axial ZTE alloys.

Metatorbernite [Cu(UO2)2(PO4)2·8H2O] is a promising remediation material for environmental uranium contamination. Previous X-ray diffraction studies have been unable to definitively locate hydrogen positions within metatorbernite, which are key to determining the hydrogen-bond network that helps to stabilize the structure. Here, hydrogen positions have been determined using a combination of neutron powder diffraction and the computational modelling technique ab initio random structure searching (AIRSS). Atomic coordinates determined through Rietveld analysis of neutron powder diffraction data are in excellent agreement with the minimum energy configuration predicted by AIRSS; thus, simulations confirm that our proposed model likely represents the global minimum configuration. Two groups of water molecules exist within the metatorbernite structure: free water and copper-coordinating water. Free water molecules are held within the structure by hydrogen bonding only, whilst the coordinating water molecules bond to copper in the equatorial positions to produce a 4 + 2 Jahn–Teller octahedra. The successful agreement between neutron powder diffraction data and AIRSS suggests that this combined approach has excellent potential for the study of other (trans)uranium materials in which hydrogen bonding plays a key role in phase stability.

This article focuses on the Na2O-Ga2O3-TiO2 system, which is barely explored in the study of transparent conductive oxides (TCOs). NaxGa4+xTin−4−xO2n−2 (n = 5, 6, and 7 and x ≈ 0.7–0.8) materials were characterized using neutron powder diffraction and aberration-corrected scanning transmission electron microscopy. Activation energy, as a function of different structures depending on tunnel size, shows a significant improvement in Na+ ion conduction from hexagonal to octagonal tunnels. New insights into the relationship between the crystal structure and the transport properties of TCOs, which are crucial for the design and development of new optoelectronic devices, are provided.

The neutron diffraction studies of powder samples from the family of A2MnTeO6 tellurates (А = Ag, Tl) were performed at room and low temperatures. The specific features of their crystal structure were investigated, and the partial substitution of Mn and Te atoms was revealed. The spin structure of Ag2MnTeO6 was determined in an ordered state at Т = 1.6 K by symmetry and full-profile analysis. It represented a non-collinear 120° triangular structure in the ab plane and a spin helicoid along the c-axis with the propagation vector k = (1/3 1/3 1/3). The neutron diffraction measurements of Tl2MnTeO6 did not reveal any additional reflections associated with the organization of long-range magnetic order up to Т = 1.6 K. The studied compounds were compared with the powders belonging to the same family and the earlier published results, which served to reveal a similarity between their crystal and magnetic structures and Na2MnTeO6 and a radically different type of their magnetic ordering as compared to Li2MnTeO6. [ABSTRACT FROM AUTHOR]

[Display omitted] • The magnetic, atomic and microstructural order largely depends on the heat treatment and composition. • A record magnetisation change of 110 Am2kg−1 was obtained around the martensitic transformation. • The magnetocaloric performance is strongly related to atomic, magnetic and microstructural ordering. • The magnetocaloric effect is driven by the formation kinetics of the L2 1 austenite phase, ferromagnetic interactions influenced by their atomic occupancy, and the residual stress present in the samples. Co-doped NiMnSn Heusler-type metamagnetic shape memory alloys (MMSMAs) are promising materials for the next-generation solid-state refrigeration systems due to their excellent magnetocaloric performance around the martensitic transformation, which is easily tuneable by slight changes in the alloy composition. An improvement in the thermal efficiency of active magnetic regenerator devices, a key element in magnetocaloric cooling systems, arises by obtaining powdered magnetocaloric alloys that meet technical requirements for their implementation as a feedstock material in the additive manufacturing of 3D-printed heat exchangers. In the present work, powders of Mn-rich NiCoMnSn Heusler-type MMSMAs were obtained from their ribbon form avoiding or minimizing residual stresses, the number of defects and disorder in the crystal lattice and microstructure. Since atomic order and crystallographic structure are crucial in the transformation and magnetic properties of these alloys, a complementary structural analysis of the powders after different heat treatments was performed by powder neutron diffraction. The results show that the cubic austenitic phase of the non-heat-treated melt-spun powder exhibits a highly stressed structure, which leads to an incomplete martensitic transformation and, therefore, to the coexistence of martensitic and austenitic phases at low temperatures. The magnetic structure of the austenite phase was also determined by neutron powder diffraction, obtaining a ferromagnetic coupling between 4a and 4b Wyckoff positions in the samples analysed. It was found that a heat treatment facilitates the martensitic transformation and enables the formation of a pure martensitic phase. The observed changes in the magnetocaloric performance of the powders have been understood in terms of the differently stressed structures and their impact on the martensitic transformation. A fully completed structural transformation leads to a significant increase of the magnetisation change across the martensitic transformation and, consequently, to high values of both a magnetic field induced isothermal entropy change and refrigeration capacity. [ABSTRACT FROM AUTHOR]

In the designed (1- x)Mn 3 GaN- x Mn 3 SbN (0.2 ≤ x ≤ 0.8) heterogeneous system, modulating the non-collinear antiferromagnetic (AFM) phase transitions of antiperovskite Mn 3 GaN using thermal stress is realized for the first time. With growing the Mn 3 SbN secondary phase, the Neel temperature (T N) of Mn 3 GaN phase shifts down by 40 K and then disappears, but another magnetic transition below T N appears and shifts up by 125 K. The neutron powder diffraction (NPD) results of the sample with x = 0.6 show that the magnetic transition below T N ascribed to the decreasing Mn–Mn distance (d Mn–Mn) and spin re-orientation from Γ5g to a new non-collinear M 2 AFM phase. By the NPD analysis, the d Mn–Mn of the Mn 3 GaN phase decreases from 2.75527(4) Å to 2.73925(3) Å, and the angles of the spin rotations for Mn1/Mn2, Mn3-1, and Mn3-2 atoms in M 2 AFM during the spin re-orientation process are 90°, 60°, and 60°, respectively. Negative thermal expansion behaviors and caloric effects associated with Γ5g phase transitions are investigated systematically. Further, the thermal stress could be regulated by adjusting the proportion of Mn 3 GaN and Mn 3 SbN phases with mismatched thermal expansion, which could be estimated even up to GPa according to Clausius–Clapeyron relation. [ABSTRACT FROM AUTHOR]

Samples with inversion parameter values (δ) ranging from 0.27 to 0.14 while maintaining the crystallite size value have been successfully fabricated from commercially available powders by mechanical grinding and thermal annealing treatments at temperatures ranging between 400 and 600 °C. Detailed characterization studies of these samples using X-ray, neutron diffraction and magnetic measurements have confirmed for the first time the simultaneous coexistence at 2 K of short range antiferromagnetic and ferrimagnetic ordering for a wide range of the inversion parameter. The magnetic phase diagram obtained is different from the one previously reported, which shows at 2 K the coexistence of long range antiferromagnetic order and short range order for values of inversion parameters less than 0.1 and the presence of a ferrimagnetic order only for values of δ > 0.2. At room temperature, the Rietveld analysis of NPD patterns and the magnetization curves showed a paramagnetic behavior in the samples with δ ≤ 0.1. For the samples with higher cationic inversion, typical hysteresis curves of ferrimagnetic materials were observed and the saturation magnetization values obtained agree quite well with the net magnetic moment obtained from the Rietveld refinement of the neutron diffraction patterns. [ABSTRACT FROM AUTHOR]

Phenol hemihydrate, C5H5OH·0.5H2O, crystallizes in the space group Pbcn, Z = 8. The previously published crystal structure [CSD refcode PHOLHH; Meuthen & von Stackelberg (1960). Z. Elektrochem. 64, 387–390] is shown to be incorrect. Pairs of phenol molecules, related by an inversion centre, are bridged by one water molecule via O—H...O hydrogen bonds; an extended R44(8) hydrogen-bonded motif links these inversion dimers into chains parallel to the c axis. Packing of the chains is achieved by weaker T-shaped C—H...π interactions between nearest neighbour phenol molecules in the bc plane. Analysis of the thermal expansion and parameterization with a Debye model in terms of the linear elastic moduli shows that the c axis is ∼3 times stiffer than the two orthogonal directions.

The structure and oxygen permeability of SrCo0.9-xNb0.1SnxO3–δ (x = 0, 0.03, and 0.05) perovskite membranes were systematically investigated by co-doping the B-site of SrCoO3–δ oxide with Nb and Sn. Combined X-ray and neutron diffraction experiments showed that all materials crystallized in the tetragonal P4/mmm space group and that the crystal structures approached the ideal cubic perovskite structure with increasing Sn concentration. In addition, X-ray photoelectron spectra confirmed that Sn-doping increases the (Co, Nb, Sn)-O bond strengths. The impact of Sn-doping on the oxygen transport of dense SrCo0.9-xNb0.1SnxO3–δ membranes was also investigated, under air/He gradient, as a function of both temperature and membrane thickness. The results showed that the oxygen transport of SrCo0.9Nb0.1O3–δ is governed by oxygen ion diffusion, while the oxygen surface exchange reaction is the limiting process for the Sn-doped membranes, SrCo0.87Nb0.1Sn0.03O3–δ and SrCo0.85Nb0.1Sn0.05O3–δ.

In this paper, the ternary system La2O3-TiO2-Nb2O5 is studied to find new ternary phases with useful electrical properties. The solid solution La3−xTi5−3xNb10−2xO39.5−12.5x was recently identified, and this study focuses on the structural characterization of this solid solution with x = 0.04. The crystal structure, representing a new structural type, was determined from synchrotron and neutron powder diffraction data. The unit cell parameters are a = 7.332 Å, b = 7.421 Å, c = 10.673 Å, α = 84.15°, ß = 80.16°, γ = 60.37°, and space group P1¯. The titanium and niobium atoms are disordered in five different crystallographic sites coordinated octahedrally by oxygen atoms. The eight-coordinated La atoms are embedded in the octahedral framework. Ti and Nb preferentially occupy different sites, and this feature was studied using periodic density functional theory methods. Energies of possible Ti/Nb distributions were calculated and the results agree well with the site occupancies obtained by combined Rietveld refinement of synchrotron and neutron powder diffraction patterns. The geometries optimized by DFT also agree well with the structural parameters determined by diffraction. The general agreement between the theoretical calculations and the experimental data justifies the quantum chemical methods as reliable complementary tools for the structural investigation of ceramic materials.

The present work is focused on the studies of the phase-structural transformations in the La 3-x Mg x Ni 9 (x ​= ​1.0, 1.1 and 1.2) alloys as active materials of negative electrodes in the Nickel-Metal Hydride (Ni/MH) batteries. The phase equilibria and phase-structural transformations in the alloys were probed by in situ neutron powder diffraction (NPD) at the temperatures ranging from 300 ​K to 1273 ​K using the measurements of the equilibrated alloys at 8 setpoint temperatures of 300, 973, 1073, 1123, 1173, 1223, 1248 and 1273 ​K. Prepared by induction melting initial alloys were found to be multi-phase structured, containing up to 6 individual intermetallic compounds with different stoichiometric compositions. With the increase of the temperature and holding time, various transformations took place in the studied alloys. These included the formations and transformations of super-stacking intermetallics with variable ratios (La ​+ ​Mg)/Ni, 1:3, 2:7 and 5:19. With increasing temperatures, several systematic changes took place. (a) Abundances of (La,Mg) 2 Ni 4 AB 2 and (La,Mg)Ni 3 AB 3 type intermetallics gradually decreased before they melted/decomposed above 1073 ​K; (b) The (La,Mg) 2 Ni 7 A 2 B 7 type intermetallics began to decrease in abundances above 1123 ​K; (c) The transformation in the (La,Mg) 5 Ni 19 intermetallics from 3R to 2H proceeded above 1223 ​K. The increase of Mg content had no obvious influence on (La,Mg) 2 Ni 4 and (La,Mg) 2 Ni 7 phases, and corresponding reactions R1 and R3 took place at the same temperatures as in the La–Ni system. However, with increasing Mg content the melting point of (La,Mg) 5 Ni 19 phase increased while the melting point of the (La,Mg)Ni 3 phase it decreased, leading to the variation of the reaction temperatures of the corresponding processes. The present study will assist in optimizing phase-structural composition of the alloys in the La–Mg–Ni system which contain Mg-modified layered structures by tailoring the high temperature annealing conditions. [Display omitted] • Transformations in the La 3-x Mg x Ni 9 (x ​= ​1.0, 1.1 and 1.2) alloys were studied by in situ NPD at 300–1273 ​K. • Initial alloy is multi-phase structured containing up to six different intermetallics with five stoichiometric compositions. • Various transformations take place on heating, leading to the disappearance of LaNi5 and LaMgNi 4. • The increase of Mg content has different influences on the intermetallics and affects on the five peritectic reactions. • The results guide optimization of phase-structural composition of La–Mg–Ni alloys by tailoring high temperature annealing conditions. [ABSTRACT FROM AUTHOR]

Among chalcogenide thermoelectric materials, SnTe is an excellent candidate for intermediate temperature applications, in replacement of toxic PbTe. We have prepared pure polycrystalline SnTe by arc melting, and investigated the structural evolution by temperature-dependent neutron powder diffraction (NPD) from room temperature up to 973 K. In this temperature range, the sample is cubic (space group Fm-3m) and shows considerably larger displacement parameters for Te than for Sn. The structural analysis allowed the determination of the Debye model parameters and provided information on the Sn–Te chemical bonds. SEM images show a conspicuous nanostructuration in layers below 30 nm thick, which contributes to the reduction of the thermal conductivity down to 2.5 W/m·K at 800 K. The SPS treatment seems to reduce the number of Sn vacancies, thus diminishing the carrier density and increasing the Seebeck coefficient, which reaches 60 μV K−1 at 700 K, as well as the weighted mobility, almost doubled compared with that of the as-grown sample.

AgSbTe2 intermetallic compound is a promising thermoelectric material. It has also been described as necessary to obtain LAST and TAGS alloys, some of the best performing thermoelectrics of the last decades. Due to the random location of Ag and Sb atoms in the crystal structure, the electronic structure is highly influenced by the atomic ordering of these atoms and makes the accurate determination of the Ag/Sb occupancy of paramount importance. We report on the synthesis of polycrystalline AgSbTe2 by arc-melting, yielding nanostructured dense pellets. SEM images show a conspicuous layered nanostructuration, with a layer thickness of 25–30 nm. Neutron powder diffraction data show that AgSbTe2 crystalizes in the cubic Pm-3m space group, with a slight deficiency of Te, probably due to volatilization during the arc-melting process. The transport properties show some anomalies at ~600 K, which can be related to the onset temperature for atomic ordering. The average thermoelectric figure of merit remains around ~0.6 from ~550 up to ~680 K.

Conditions for YBaFe 4 O 7 synthesis from oxide/carbonate amorphous precursors are investigated versus temperature and partial pressure of oxygen at high-temperature equilibrium with the sample in flowing atmosphere of humidified Ar and H 2 gas mixtures. Upon topotactic oxidation in ambient air of the cooled-down product, YBaFeIII 4 O 8.5 forms in a couple of minutes. Neutron powder diffraction suggests that added oxygens enter octahedral holes in the cubic closest packing of O and Ba atoms of YBaFe 4 O 7. Up to two oxygen atoms add to some Fe coordination tetrahedra in the kagome-like layer of YBaFe 4 O 7 in a disordered distribution described as partially occupied crystal-structure sites. The oxidized YBaFeIII 4 O 8.5 is metastable and decomposes at high temperatures into FeIII oxides of barium or yttrium. The synthesized YBaFe 4 O 7 is a powerful room-temperature O 2 getter that can be reverted by annealing in the above gas mixture. [Display omitted] • Formation limits of YBaFe 4 O 7 under calcination of amorphous precursor. • Its topotactic oxidation in ambient air into metastable YBaFeIII 4 O 8.5 • YBaFe 4 O 7 at room temperature is a powerful O 2 gas getter. • Neutron powder diffraction of YBaFeIII 4 O 8.5 with partial oxygen disorder. [ABSTRACT FROM AUTHOR]

Bismuth ferrite (BiFeO3) was synthesized by hydrothermal method. The crystal and magnetic structures of BiFeO3 have been studied by means of X-ray diffraction and neutron powder diffraction at ambient temperature. Microstructure was analysed by scanning electron microscopy. Quantitative phase analysis by the Rietveld method was conducted and crystallite sizes of 27 nm were determined from the XRD line broadening. The magnetic structure of BiFeO3 is described by the G-type antiferromagnetic order with magnetic peak located at 4.6 Å and a noticeable magnetic contribution to a reflection located at 2.4 Å in the diffraction pattern. The values of the ordered magnetic moment of Fe ions μFe=3.8(1) μB, obtained at ambient conditions, are consistent with those determined earlier. The magnetic moments in the crystal plane z = const are arranged in parallel, changing the direction from [100] to [110¯] when moving from one to the other z = const plane. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45012]