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The nuclear and magnetic structures of CaxSr2−xWMnO6 (x = 0.5, 1.0, 1.5) have been investigated by neutron diffraction at 295, 30 or 40 K, and 4 or 5 K. The compounds crystallized in the monoclinic symmetry with a space group P21/n. The nuclear structure consists of ordered WO6 and Mn2+O6 octahedral frameworks, with lattice constant a decreasing more rapidly than b with increasing Ca content. No structural change was found around the magnetic transition temperature, although the Mn octahedron below the magnetic order temperature exhibited a slightly compressed Jahn–Teller distortion (0.1–0.3 Å) along the c axis. A standard magnetic model was used to solve the magnetic structure, with the Mn magnetic moments ferromagnetically coupled along the a axis and anti-ferromagnetically coupled along the b and c axes, resulting in a magnetic propagation vector of k = (0,1/2, 1/2) and a magnetic superlattice of 1a × 2b × 2c. In each crystallographic cell, the Mn1–Mn2 atoms are antiferromagnetically configurated, compensating the total moment to zero by symmetry. A layer-type magnetism along the (111) crystallographic plane was confirmed to couple antiferromagnetically between these planes and ferromagnetically within them. The magnetic structure refinement confirmed an average Mn moment of 4.5 μB. Also, it reveals that the collinear magnetic Mn configuration has three possible spin orientations, namely, (with their standard deviation) [μx = (3.3 ± 0.4) μB, μy = (2.5 ± 0.3) μB, μz = (−0.7 ± 0.7) μB], [μx = (3.0 ± 0.4) μB, μy = (0.5 ± 0.2) μB, μz = (−2.8 ± 0.2) μB, and [μx = (−1.8 ± 0.4) μB, μy = (2.9 ± 0.2) μB, μz = (−2.4 ± 0.3) μB. The first configuration is estimated to be the ground state, while the other magnetic configurations are an optimum local value derived from the refinements. Combined with the density functional theory calculations, these experimental results confirm a high-spin state Mn2+ (d5) electron configuration. [ABSTRACT FROM AUTHOR]

Abstract: The crystal and magnetic structures of SrFe2+ 2(PO4)2 have been determined by neutron powder diffraction data at low temperatures (space group P21/c (no. 14); Z=4; a=9.35417(13)Å, b=6.83808(10)Å, c=10.51899(15)Å, and β=109.5147(7)° at 15K). Two magnetic phase transitions were found at T 1=7.4K (first-order phase transition) and T 2=11.4K (second-order phase transition). The transition at T 2 was hardly detectable by dc and ac magnetization measurements, and a small anomaly was observed by specific heat measurements. At T 1, strong anomalies were found by dc and ac magnetization and specific heat. The structure of SrFe2(PO4)2 consists of linear four-spin cluster units, Fe2–Fe1–Fe1–Fe2. Below T 1, the propagation vector of the magnetic structure is k=[0,0,0]. The magnetic moments of the inner Fe1–Fe1 atoms of the four-spin cluster unit are ferromagnetically coupled. The magnetic moment of the outer Fe2 atom is also ferromagnetically coupled with that of the Fe1 atom but with spin canting. The four-spin cluster units form ferromagnetic layers parallel to the [−101] plane, while these layers are stacked antiferromagnetically in the [−101] direction. Spin canting of the outer Fe2 atoms provides a weak ferromagnetic moment of about 1 μ B along the b-axis. The refined magnetic moments at 3.5K are 4.09 μ B for Fe1 and 4.07 μ B for Fe2. Between T 1 and T 2, a few weak magnetic reflections were observed probably due to incommensurate magnetic order. [Copyright &y& Elsevier]

A new form of LiMn2O4 is reported. The structure is the CaFe2O4-type and 6% denser than the spinel. The structure transformation was achieved by heating at 6 GPa. Analysis of the neutron diffraction pattern confirmed an average of the structure; the unit cell was orthorhombic at a = 8.8336(5) Å, b = 2.83387(18) Å, and c = 10.6535(7) Å (Pnma). Electron diffraction patterns indicated an order of superstructure 3a × b × c, which might be initiated by Li vacancies. The exact composition is estimated at Li0,92Mn2O4 from the structure analysis and quantity of intercalated Li. The polycrystalline CaFe2O4-type compound showed semiconducting-like characters over the studied range above 5 K. The activation energy was reduced to ∼0.27 eV from ∼0.40 eV at the spinel form, suggesting a possible enhancement of hopping mobility. Magnetic and specific-heat data indicated a magnetically glassy transition at ∼10 K. As the CaFe2O4-type transition was observed for the mineral MgAl2O4, hence the new form of the lithium manganese oxide would provide valuable opportunities to study not only the magnetism of strongly correlated electrons but also the thermodynamics of the phase transition in the mantle. [ABSTRACT FROM AUTHOR]

The magnetic ordering of the tetragonal Ca14MnSb11 compound (space group I41/acd) has been determined by high-resolution neutron diffraction on powder samples. Neutron data were obtained at temperatures of 1.4, 10, 95 K, and room temperature. Refinement of the magnetic structure reveals a ferromagnetic ordering of Mn magnetic moments lying in the a–b plane below the TC of 63 K. The low-temperature-ordered magnetic moment on the Mn ion is 3.4(2) μB at 1.4 K. The results are confirmed by magnetic susceptibility measurements, which show that the easy magnetization direction of the compound is perpendicular to the c-axis and the system orders ferromagnetically at 63 K, in good agreement with neutron diffraction results. A large negative magnetoresistance effect (Δρ/ρ(H)=−34.4%) at the magnetic transition temperature is observed in applied magnetic fields up to 6 T. [Copyright &y& Elsevier]

Chemical ordering is a common phenomenon and highly correlated with the properties of solid materials. By means of the redistribution of atoms and chemical bonds, it invokes an effective lattice adjustment and tailors corresponding physical properties. To date, however, directly probing the 3D interfacial interactions of chemical ordering remains a big challenge. In this work, we deciphered the interlaced distribution of nanosized domains with chemical order/disorder in Fe3Pt bulk alloy. HAADF-STEM images evidence the existence of such nanodomains. The reverse Monte Carlo method with the X-ray pair distribution function data reveal the 3D distribution of local structures and the tensile effect in the disordered domains at the single-atomic level. The chemical bonding around the domain boundary changes the bonding feature in the disordered side and reduces the local magnetic moment of Fe atoms. This results in a suppressed negative thermal expansion and extended temperature range in Fe3Pt bulk alloy with nanodomains. Our study demonstrates a local revelation for the chemical order/disorder nanodomains in bulk alloy. The understanding gained from atomic short-range interactions within the domain boundaries provides useful insights with regard to designing new functional compounds. [ABSTRACT FROM AUTHOR]

Sulfur mustard (SM), a chemical warfare agent, can form adducts with DNA, RNA, and proteins. Reactions with DNA lead to the formation of both DNA monoadducts and interstrand cross-links, resulting in DNA damage, and is an important component of SM toxicity. Our previous in vivo studies indicated that dividing cells such as hematopoietic stem cells and intestinal villi stem cells seemed to have increased sensitivity to SM. Therefore, to compare the sensitivity of somatic and stem cells to SM and to investigate the mechanism of SM cytotoxicity, we isolated human foreskin fibroblasts, reprogrammed them into pluripotent stem cells, and then compared the DNA damage repair pathways involved upon SM treatment. Our results indicated that proliferating stem cells were more sensitive to SM-induced DNA damage, and the damage mainly comprised single-stranded breaks. Furthermore, the pathways involved in DNA repair in stem cells and somatic cells were different. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of the ThCr2Si2-type solid solution LaMn2(Ge1−xSix)2 (x = 0.0 to 1.0) have been investigated employing a combination of X-ray diffraction, magnetization and neutron diffraction measurements, which allowed establishing a magnetic composition-temperature phase diagram. Substitution of Ge by Si leads to a compression of the unit cell, which affects the magnetic exchange interactions. In particular, the magnetic structure of LaMn2(Ge1−xSix)2 is strongly affected by the unit cell parameter c, which is related to the distance between adjacent Mn layers. Commensurate antiferromagnetic layers and a canted ferromagnetic structure dominate the Si-rich part of the solid solution, whilst an incommensurate antiferromagnetic flat spiral and a conical magnetic structure are observed in the Si-poor part. [ABSTRACT FROM AUTHOR]

The nuclear and magnetic structures of the cubic antiperovskite compound Mn3NiN are studied using neutron powder diffraction as a function of temperature and applied magnetic field. On cooling in zero field from the paramagnetic state, an anomalous lattice expansion abruptly occurs as the long range antiferromagnetic order first develops below TN = 262 K. The magnetic structure has lower symmetry than the crystal and can be conveniently described by a rhombohedral R-3 symmetry with dimension of [Square_Root]2ac × [Square_Root]2ac × [Square_Root]3ac, where ac is the chemical unit cell. In this description, the magnetic moment of the Mn is restricted to the a-b plane, but continuously rotates from 90° to around 38° as the temperature decreases to ≈120 K, below which the spin directions remain fixed. The combined magnetic and structural transition exhibits a very large magnetovolume effect with an entropy change of ΔS ≈ 54 J/kg K, but the application of a 6 T magnetic field has little effect on the magnetic structure or entropy change. The crystallographic results indicate that the properties can be tailored by small changes in the composition and site vacancies, and the results enrich the understanding of the magnetostrictive effects in antiperovskites. [ABSTRACT FROM AUTHOR]

We first found that ScCo(CN) 6 of Prussian blue analogues has a large isotropic negative thermal expansion which occurs in a wide temperature range from 25K to 600K. More intriguingly, the present material of ScCo(CN) 6 exhibits the merits of the facile fabrication via chemical coprecipitation and the good environment stability of water-free, which are very important for the applications. The transverse vibration of C and N atoms is critical for the occurrence of negative thermal expansion, which is confirmed by the atomic mean square relative displacements. The present new material of ScCo(CN) 6 will be promising for the applications. Image, graphical abstract [ABSTRACT FROM AUTHOR]

By a simple cross-substitution of A-site Li/Na in tetragonal tungsten bronze (TTB) structures, we successfully synthesized a new niobate compound, Pb2.15(Li0.25Na0.75)0.7Nb5O15, with a superstructure. This compound exhibits a strong second harmonic generation (SHG) up to ∼47 × KDP. The large SHG response is related to strengthened local distortion, manifesting cross-substitution as a possibly general route to improve the NLO effect in stiff and low symmetric structures. [ABSTRACT FROM AUTHOR]

The compound Mn1.1Fe0.9P0.76Ge0.24 has been studied using neutron powder diffraction (NPD), differential scanning calorimeter (DSC), and magnetic measurements, in order to clarify the nature of the magnetic and structural transition and measure the associated entropy change (ΔS). The strongly first order transition occurs from a paramagnetic (PM) to a ferromagnetic (FM) phase and can be induced either by temperature or by an applied magnetic field. Our investigations indicate that the two processes exhibit identical evolutions regarding the crystal and magnetic structures, indicating they should have the same entropy change. We, therefore, conclude that the ΔSDSC obtained by the DSC method (where the transition is temperature induced) is valid also for the magnetically induced transition, thus avoiding uncertainties connected with the magnetic measurements. We have obtained the ΔSDSC = 33.8 J/kg · K for this sample upon cooling, which would increase to 42.7 J/kg · K for a impurity-free and completely homogeneous sample. For comparison, the magnetic entropy changes (ΔSM) induced by magnetic field and calculated using the Maxwell relation yields a ΔSM = 46.5J/kg · K, 38% higher than ΔSDSC. These entropy results are compared and discussed. [ABSTRACT FROM AUTHOR]

Bi2NiTiO6 compound which shows both magnetic (TM = 58 K) and ferroelectric properties (TC = 513 K) was synthesized under high pressure of 5 GPa and temperature of 1273 K. The crystal structure, as determined by X-ray powder diffraction and neutron powder diffraction, is a distorted A(B1B2)O3 type perovskite with space group Pn21a. Structural evolution of multiferroic Bi2NiTiO6 shows that there are two isostructural phase transitions at ∼2 GPa and ∼15 GPa under high pressure and at room temperature and indicates that isostructural phase transitions occurred with temperature higher than 823 K under ambient condition. All the isostructural phase transitions come from the Bi ion discontinuous shift, which identifies the phase transition at ∼15 GPa and at temperature higher than 823 K are the same. Using a modified high-T Birch-Murnaghan equation of state and a thermal-pressure approach, we have derived the thermoelastic parameters of high pressure phase Bi2NiTiO6, including the ambient bulk modulus K0, temperature derivative of bulk modulus at constant pressure, volumetric thermal expansivity, pressure derivative of thermal expansion, and temperature derivative of bulk modulus at constant volume. [ABSTRACT FROM AUTHOR]

The antiperovskite Mn 3 Zn 0.77 Mn 0.19 N 0.94 was investigated by in situ neutron powder diffraction (NPD) in the temperature region 5–300 K. Here, a noncollinear-antiferromagnetic/collinear-ferrimagnetic phase separation (PS) showing different lattice parameters was firstly revealed in antiperovskites. The NPD results prove that the noncollinear antiferromagnetic phase, even coexisting with the collinear ferrimagnetic phase, could be responsible for the zero thermal expansion behavior of Mn 3 Zn 0.77 Mn 0.19 N 0.94 below 110 K. These findings suggest that Mn 3 ZnN based materials could open a new avenue for further exploring the noncollinear magnetic PS and correlated physical properties of antiperovskites. [ABSTRACT FROM AUTHOR]

Hybrid iron-based superconductors were synthesized by sonochemical insertion of organic molecules into FeSe layers. High quality of the samples first enabled reliable phase identifications and three structure types were discovered. Structure determination based on neutron data further facilitated the understanding of their structural stability, doping levels and temperature driven structural transitions. [ABSTRACT FROM AUTHOR]

The control of thermal expansion of solid compounds is intriguing but remains challenging. The effect of guests on the thermal expansion of open-framework structures was investigated. Notably, the presence of guest ions (K+) and molecules (H2O) can substantially switch thermal expansion of YFe(CN)6 from negative ( αv=−33.67×10−6 K−1) to positive ( αv=+42.72×10−6 K−1)-a range that covers the thermal expansion of most inorganic compounds. The mechanism of such substantial thermal expansion switching is revealed by joint studies with synchrotron X-ray diffraction, X-ray absorption fine structure, neutron powder diffraction, and density functional theory calculations. The presence of guest ions or molecules plays a critical damping effect on transverse vibrations, thus inhibiting negative thermal expansion. An effective method is demonstrated to control the thermal expansion in open-framework materials by adjusting the presence of guests. [ABSTRACT FROM AUTHOR]

The control of thermal expansion of solid compounds is intriguing but remains challenging. The effect of guests on the thermal expansion of open-framework structures was investigated. Notably, the presence of guest ions (K+) and molecules (H2O) can substantially switch thermal expansion of YFe(CN)6 from negative ( αv=−33.67×10−6 K−1) to positive ( αv=+42.72×10−6 K−1)-a range that covers the thermal expansion of most inorganic compounds. The mechanism of such substantial thermal expansion switching is revealed by joint studies with synchrotron X-ray diffraction, X-ray absorption fine structure, neutron powder diffraction, and density functional theory calculations. The presence of guest ions or molecules plays a critical damping effect on transverse vibrations, thus inhibiting negative thermal expansion. An effective method is demonstrated to control the thermal expansion in open-framework materials by adjusting the presence of guests. [ABSTRACT FROM AUTHOR]

Polycrystalline monoclinic Er 12 Co 7 compound with a large magnetocaloric effect (MCE) was synthesized. The maximum values of the magnetic entropy change (ΔS M ) under the field changes of 0–2 T and 0–5 T reach 10.2 J/kgK and 18.3 J/kgK, respectively. In order to gain further insight in understanding the MCE, samples with various Ho substitutions for Er were fabricated and studied. It was found that Ho-substitution makes a great impact on the magnetic properties and MCE of Er 12 Co 7 compound. Through compositional optimization, the mixed product of Ho 12 Co 7 and Er 6 Ho 6 Co 7 with the weight ratio of 58:42 was tailored to exhibit the best MCE performance. The maximum value of ΔS M , the full width at half maximum of ΔS M -T curve and the refrigerant capacity of the mixed compound are calculated to be 16.7 J/kgK, 37.9 K and 522 J/kg, respectively. [ABSTRACT FROM AUTHOR]

The first transition-metal-only double perovskite compound, Mn2+2Fe3+Re5+O6, with 17 unpaired d electrons displays ferrimagnetic ordering up to 520 K and a giant positive magnetoresistance of up to 220 % at 5 K and 8 T. These properties result from the ferrimagnetically coupled Fe and Re sublattice and are affected by a two-to-one magnetic-structure transition of the Mn sublattice when a magnetic field is applied. Theoretical calculations indicate that the half-metallic state can be mainly attributed to the spin polarization of the Fe and Re sites. [ABSTRACT FROM AUTHOR]

The first transition-metal-only double perovskite compound, Mn2+2Fe3+Re5+O6, with 17 unpaired d electrons displays ferrimagnetic ordering up to 520 K and a giant positive magnetoresistance of up to 220 % at 5 K and 8 T. These properties result from the ferrimagnetically coupled Fe and Re sublattice and are affected by a two-to-one magnetic-structure transition of the Mn sublattice when a magnetic field is applied. Theoretical calculations indicate that the half-metallic state can be mainly attributed to the spin polarization of the Fe and Re sites. [ABSTRACT FROM AUTHOR]

Theorigin of transition metal vacancies and their effects on theproperties of ThCr2Si2-type compounds have beenless studied and poorly understood. Here we carefully investigatethe structure, physical properties, and electronic structure for aseries of lanthanum cobalt arsenides with nominal composition of LaCoxAs2(1.6 ≤ x≤ 2.1). It is revealed that the occupancy of Co can be tunedbetween 1.98(1) and 1.61(1). The structural analyses based on X-rayand neutron diffractions show the existence of Co vacancies resultsfrom charge balance due to the formation of bond between As–As.These Co vacancies affect the magnetic and electrical properties greatly,adjusting the Curie temperature from 205 to 47 K and increasing theresistivity by more than 100%. First-principles calculations indicatethat the Co vacancies weaken the spin polarization and reduce thedensity of states at the Fermi level, resulting in decreased Curietemperature and increased resistivity, respectively. Our results addressthe importance of transition metal vacancies in ThCr2Si2-type materials and offer a reliable route to tune the magnetismof ThCr2Si2-type structure. [ABSTRACT FROM AUTHOR]

Abstract: We report a large magnetic entropy change observed in the antiperovskite Mn3Cu0.89N0.96. Based on the heat flow peak measured by differential scanning calorimetry, the total entropy change according to the structural transition (tetragonal to cubic) was calculated to be ∼60Jkg–1 K–1 while the magnetic entropy change accounts for ∼22.5% of the total entropy under a 50kOe magnetic field at 145K. To clarify the origin of the magnetic entropy change, we managed to control the structure transition using a magnetic field. It was found that the magnetic entropy change originates from the transformation from antiferromagnetic (AFM) to ferromagnetic (FM) as well as from the phase transition from cubic to tetragonal under the magnetic field. In the tetragonal phase, a magnetic field can drive the AFM component to transform gradually to the FM component. The magnetic field can also change the phase fraction in the tetragonal and cubic two-phase coexistence region, a similar behavior to that induced by temperature. In the current system, only 5.4% of the cubic phase transforms to the tetragonal phase at 5Tesla (T), indicating there is still much latent entropy in Mn3Cu0.89N0.96. [Copyright &y& Elsevier]

Single-phase polycrystalline solid solutions (La1− xSm x)B6 ( x = 0, 0.2, 0.4, 0.8, 1) are fabricated by spark plasma sintering (SPS). This study demonstrates a systematic investigation of structure-property relationships in Sm-doped LaB6 ternary rare-earth hexaborides. The microstructure, crystallographic orientation, electrical resistivity, and thermionic emission performance of these compounds are investigated. Analysis of the results indicates that samarium (Sm) doping has a noticeable effect on the structure and performance of lanthanum hexaboride (LaB6). The analytical investigation of the electron backscatter diffraction confirms that (La0.6Sm0.4)B6 exhibits a clear (001) texture that results in a low work function. Work functions are determined by pulsed thermionic diode measurements at 1500-1873 K. The (La0.6Sm0.4)B6 possesses improved thermionic emission properties compared to LaB6. The current density of (La0.6Sm0.4)B6 is 42.4 A cm−2 at 1873 K, which is 17.5% larger than that of LaB6. The values of ΦR for (La0.6Sm0.4)B6 and LaB6 are 1.98 ± 0.03 and 1.67 ± 0.03 eV, respectively. Furthermore, the Sm substitution of lanthanum (La) effectively increases the electrical resistivity. These results reveal that Sm doping lead to significantly enhanced thermionic emission properties of LaB6. The compound (La0.6Sm0.4)B6 appears most promising as a future emitter material. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis, structure, and elementary magnetic and electronic properties are reported for layered compounds of the type Na3−x MIr2O6 and Na3−x M 2IrO6, where M is a transition metal from the 3d series (M=Zn, Cu, Ni, Co, Fe and Mn). The rhombohedral structures, in space group R−3m, were determined by refinement of neutron and synchrotron powder diffraction data. No clear evidence for long range 2:1 or 1:2 honeycomb-like M/Ir ordering was found in the neutron powder diffraction patterns except in the case of M=Zn, and thus in general the compounds are best designated as sodium deficient α-NaFeO2-type phases with formulas Na1−x M 1/3Ir2/3O2 or Na1−x M 2/3Ir1/3O2. Synchrotron powder diffraction patterns indicate that several of the compounds likely have honeycomb in-plane metal–iridium ordering with disordered stacking of the layers. All the compounds are sodium deficient under our synthetic conditions and are black and insulating. Weiss constants derived from magnetic susceptibility measurements indicate that Na0.62Mn0.61Ir0.39O2, Na0.80Fe2/3Ir1/3O2, Na0.92Ni1/3Ir2/3O2, Na0.86Cu1/3Ir2/3O2, and Na0.89Zn1/3Ir2/3O2 display dominant antiferromagnetic interactions. For Na0.90Co1/3Ir2/3O2 the dominant magnetic interactions at low temperature are ferromagnetic while at high temperatures they are antiferromagnetic; there is also a change in the effective moment. Low temperature specific heat measurements (to 2K) on Na0.92Ni1/3Ir2/3O2 indicate the presence of a broad magnetic ordering transition. X-ray absorption spectroscopy shows that iridium is at or close to the 4+ oxidation state in all compounds. 23Na nuclear magnetic resonance measurements comparing Na2IrO3 to Na0.92Ni1/3Ir2/3O2 and Na0.89Zn1/3Ir2/3O2 provide strong indications that the electron spins are short-range ordered in the latter two materials. Na0.62Mn0.61Ir0.39O2, Na0.80Fe2/3Ir1/3O2, Na0.90Co1/3Ir2/3O2, Na0.92Ni1/3Ir2/3O2, Na0.86Cu1/3Ir2/3O2 and Na0.89Zn1/3Ir2/3O2 are spin glasses. (CSD-numbers: Na0.62Mn0.61Ir0.39O2: 426657, Na0.80Fe2/3Ir1/3O2: 426659, Na0.90Co1/3Ir2/3O2: 426658, Na0.92Ni1/3Ir2/3O2: 426656, Na0.86Cu1/3Ir2/3O2: 426655, and Na2.8ZnIr2O6: 426660.) [Copyright &y& Elsevier]

The title compound is characterized by neutron diffraction at temperatures between 50 and 295 K. [ABSTRACT FROM AUTHOR]

The effects of Zn vacancies on the physical properties of antiperovskite compounds Mn3Zn x N (x =0.96 and 0.93) were investigated. For Mn3Zn0.96N, lowering the temperature produced two anomalies in the magnetization and heat capacity curves: the first at ∼185K is related to magnetic ordering and was accompanied by a lattice expansion; the second at ∼115K is due to a magnetic order change and showed a lattice contraction. However, for Mn3Zn0.93N only a single transition is observed around 185K. [ABSTRACT FROM AUTHOR]

Abstract: The phase relationship of the TbO1.81–Mn3O4–Fe2O3 pseudo-ternary system synthesized at 1200°C was determined using X-ray and neutron diffraction method. Four solid solutions, Mn3−3 x Fe3 x O4 (0.00⩽ x ⩽0.278), Mn3−3 x Fe3 x O4 (0.291⩽ x ⩽0.667), Mn2−2 x Fe2 x O3 (0.89⩽ x ⩽1.00), and (Tb1− y Mn z Fe x )(Fe w Mn1− w )O3 (1−y + x + z ⩽1, 0.00⩽ w ⩽1.00) were found along with six two-phase regions and three three-phase regions. The boundaries were determined by several different methods such as phase disappearing, the Vigard’s law, and the lever rule. [Copyright &y& Elsevier]

Neutron diffraction is used to reveal the origin and control of the thermal expansion properties of the cubic intermetallic compounds Mn3ZnxN and Mn3[Zn-(Ag,Ge)]xN. We show that the introduction of Zn vacancies induces and stabilizes an antiferromagnetic phase with huge spin-lattice coupling that can be tuned to achieve zero thermal expansion (ZTE) over a wide temperature range. We further show that the antiferromagnetic ordering temperature (TN) that controls this ZTE can be tuned by chemical substitution, again on the Zn site, to adjust the span of ZTE temperatures from well above room temperature to well below. This establishes a quantitative relationship and mechanism to precisely control the ZTE of a single material, enabling it to be tailored for specific device applications. [ABSTRACT FROM AUTHOR]

The near zero temperature coefficient of resistivity (NZ-TCR) in Mn-based antiperovskite Mn3Ni1-xCuxN is reported. The temperature range of NZ-TCR is controllable by changing Cu content. Further, the TCR value of 0.09 ppm K-1 was obtained in Mn3Ni0.5Cu0.5N over a broad temperature range around room temperature. The anomalous resistivity change of Mn3Ni1-xCuxN from metal-like to NZ-TCR behavioris apparently due to a magnetic transition. The possible reason for the formation of NZ-TCR is interpreted on the basis of spin-disorder scattering. [ABSTRACT FROM AUTHOR]

Abstract: Nanostructured polycrystalline LaB6 ceramics were prepared by the reactive spark plasma sintering method, using boron nanopowders and LaH2 powders with a particle size of about 30nm synthesized by hydrogen dc arc plasma. The reaction mechanism of sintering, crystal structure, microstructure, grain orientations and properties of the materials were investigated using differential scanning calorimetry, X-ray diffraction, Neutron powder diffraction, Raman spectroscopy, transmission electron microscopy and electron backscattered diffraction. It is shown that nanostructured dense LaB6 with a fibrous texture can be fabricated by SPS at a pressure of 80MPa and temperature of 1300°C for 5min. Compared with the coarse polycrystalline LaB6 prepared by traditional methods, the nanostructured LaB6 bulk possesses both higher mechanical and higher thermionic emission properties. The Vickers hardness was 22.3GPa, the flexural strength was 271.2MPa and the maximum emission current density was 56.81Acm−2 at a cathode temperature of 1600°C. [Copyright &y& Elsevier]

Abstract: Combined synchrotron in situ X-ray diffraction and neutron diffraction studies were performed on 2:1 mixtures of lithium amide and magnesium hydride, which have shown promise as solid-state hydrogen storage materials. The dehydrogenated product is a mixed lithium and magnesium imide, Li2Mg(NH)2, whose crystal structure has not heretofore been determined. Furthermore, at elevated temperatures, Li2Mg(NH)2 undergoes two structural transitions from an orthorhombic structure to a primitive cubic structure at intermediate temperature (350°C) followed by a face-centered cubic crystal structure at high temperature (500°C). Disordering of the Li, Mg and cation vacancies as a function of temperature drives the structural transitions. We report the reaction pathway from in situ X-ray diffraction studies and the crystal structures of the three structural variants of Li2Mg(NH)2 as determined by high-resolution X-ray and neutron powder diffraction. We also report the hydrogen storage reaction pathways for mixtures with other cation ratios. [Copyright &y& Elsevier]

The title compounds are prepared by solid-state reaction of stoichiometric amounts of Na2CO3, SnO2, and Sb2O5 (1. [ABSTRACT FROM AUTHOR]

Layered polycrystalline Na3Ni2BiO6 is prepared by firing stoichiometric amounts of Na2CO3, NaBiO3, and NiO with a 3% excess of Na for compensating volatilization losses (alumina boat, 700 °C, 8 h, flowing O2). [ABSTRACT FROM AUTHOR]

Substitution of Ni for In in InTaO4 is reinvestigated by synchrotron X-ray and neutron powder diffraction, diffuse reflectance spectroscopy, XANES, and magnetic susceptibility measurements, providing insights into its previously reported photoactivity. [ABSTRACT FROM AUTHOR]