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The crystal structure of deuterated methane hydrate (structure I, space group: Pm3n) was investigated by neutron powder diffraction at temperatures of 7.7–185 K. The scattering amplitude density distribution was examined by a combination of Rietveld method and maximum entropy method (MEM). The distribution of the D atoms in both D2O and CD4 molecules was clarified from three-dimensional graphic images of the scattering amplitude density. The MEM results showed that there were low-density sites for the D atom of D2O in a particular location within the D2O cage at low temperatures. The MEM provided more reasonable results because of the decrease in the R factor that is attainable by this method. Accordingly, the low-density sites for the D atom of D2O probably exist within the D2O cage. This suggests that a spatial disorder of the D atom of D2O occurs at these sites and that hydrogen bonds between D2O molecules become partially weakened. With regard to the CD4 molecules, there were high-density sites for the D atom of CD4, and the density distribution of the C and D atoms was observed separately in the scattering amplitude density image. Consequently, the C-D bonds of CD4 were not observed clearly because the CD4 molecules had an orientational disorder. The D atoms of CD4 were displaced from the line between the C and O atoms, and were located near the face center of the polygon in the cage. Accordingly, the D atoms of CD4 were not bonded to specific O atoms. This result is consistent with the hydrophobicity of the CD4 molecule. We also report the difference between the small and the large cages in the density distribution map and the temperature dependence of the scattering amplitude density. [ABSTRACT FROM AUTHOR]

Abstract Clathrate hydrates have a polyhedral cage structure (host structure) formed by hydrogen bond-linked water molecules, and various guest molecules can be accommodated in these cages. Methane-propane hydrate is a clathrate hydrate with a crystal structure similar to propane hydrate (structure II, cubic, Fd -3 m). The host lattice consists of small cages (S cages) and large cages (L cages). Due to their size, propane molecules (C 3 H 8) are contained only in the L cages, while methane molecules (CH 4) can be included in both the S cages and the L cages. In this report, methane-propane hydrate was synthesized at −10 °C using a pressurized gas mixture with a methane-to-propane ratio of 2:1. We estimated the filling rates of the guest molecules using a precise structure analysis including hydrogen atoms. Methane molecules were contained only in the S cages under our synthesis conditions. [ABSTRACT FROM AUTHOR]

Ceria (CeO2) was kinetically reduced in hydrogen depending on the isothermal holding time at high temperature. In situ powder neutron diffraction measurements indicated that ceria underwent structural transition to a triclinic oxygen-deficient structure during the cooling process. Oxygen vacancies were also present in the bulk phase of ceria. [ABSTRACT FROM AUTHOR]

Neutron diffraction measurements revealed that the oxyhydroxide ceria CeO2Hy (0 ≦y≦1) was formed by the interaction of hydrogen under high temperature. Ceria was kinetically reduced in hydrogen depending on the isothermal holding time, and the crystal phase of CeO2H was precipitated during the short isothermal holding time. [ABSTRACT FROM AUTHOR]

The accuracy of the phase fraction determined by time-of-flight neutron diffraction measurement at iMATERIA was verified by preparing model samples consisting of laminations of ferritic and austenitic stainless-steel sheets. Rietveld texture analysis, based on 132 diffractograms, was employed as the analysis method. The analyzed volume fractions of austenite agree with the prepared fractions (0.61-49.3 vol%) with a maximum error of only 5%, relative to the prepared fractions. This is due to the excellent fitting quality of the multi-diffractogram-based Rietveld refinement with consideration given to the textures of both the major and minor phases. Although the quality of the texture analysis for the austenite phase becomes poor, at <5 vol%, the consideration of the textures improves the accuracy of the phase fraction determination. Also described is how the textures affect the phase fractions, as determined by the conventional diffraction method. It is clearly shown that texture cannot be ignored in phase fraction analysis and, in turn, a reasonable consideration of the texture realizes precision in the analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • The crystal structure of hydrogen sulfide hydrate was investigated by powder neutron diffraction. • The scattering length density distribution estimated by the maximum entropy method revealed the anharmonic density distribution corresponding to the hydrogen bonding network. • The hydrogen bonding network changed with temperature, indicating that the guest–host interaction changed with temperature in hydrogen sulfide hydrate. Clathrate hydrates have cage-like host structures that enclose the guest molecules. Hydrogen sulfide hydrate has a lower synthesis pressure than ordinary hydrocarbon hydrates. Since hydrogen sulfide is one of the polar molecules like water, some interactions between hydrogen sulfide and water stabilize the clathrate structure. We investigated the hydrogen bonding network in hydrogen sulfide hydrate using powder neutron diffraction. The scattering length density distribution corresponding to hydrogen atoms of water molecules showed a spread from the straight line between oxygen atoms, and the distribution changed with temperature. We revealed that the hydrogen bonding network changed with temperature. [ABSTRACT FROM AUTHOR]

The crystal structure of deuterated 4-dimethylamino- N -methyl-4-stilbazolium tosylate (DAST- d 26 ) was obtained by powder X-ray and neutron diffraction measurements. The scattering length density distributions of deuterium atoms were successfully obtained from neutron diffraction data using the maximum-entropy method. From the density distributions, we estimated the hydrogen-bonding distances, which contribute significantly to the vibrational modes of DAST at 1 THz. Inhibition of these hydrogen bonds could allow the development of new nonlinear optical materials with low THz absorption. [ABSTRACT FROM AUTHOR]

A rapid texture measurement system has been developed on the time-of-flight neutron diffractometer iMATERIA (beamline BL20, MLF/J-PARC, Japan). Quantitative Rietveld texture analysis with a neutron beam exposure of several minutes without sample rotation was investigated using a duplex stainless steel, and the minimum number of diffraction spectra required for the analysis was determined experimentally. The rapid measurement scheme employs 132 spectra, and by this scheme the quantitative determination of volume fractions of texture components in ferrite and austenite cubic phases in a duplex stainless steel can be made in a short time. This quantitative and rapid measurement scheme is based on the salient features of iMATERIA as a powder diffractometer, i.e. a fairly high resolution in d spacing and numerous detectors covering a wide range of scattering angle. [ABSTRACT FROM AUTHOR]

[Display omitted] • The crystal structure of deuterated ethane hydrate was investigated by powder neutron diffraction. • A structural phase transition occurred in deuterated ethane hydrate at low temperature. • The ethane molecules were ordered in the cage structure with hexagonal symmetry. • The calculated scattering density distribution indicated the bonding density was partially weak in the hexagonal phase. Ethane hydrate, a natural gas hydrate, has been considered to only have a cubic symmetry known as structure I. Neutron diffraction measurement of deuterated ethane hydrate was performed from 10 K to 150 K. The diffraction patterns of deuterated ethane hydrate drastically changed below 30 K. A new hexagonal crystal structure with ordered ethane molecules was found as a clathrate hydrate structure. This phase transition was concerned with the thermal motion of the ethane molecules. [ABSTRACT FROM AUTHOR]

Abstract: To examine the nature of thermal motions of the CH4 molecules in the methane deuterohydrate (8CH4·46D2O), the scattering length density distribution was observed by the maximum entropy method (MEM) using neutron powder diffraction data measured in the temperature range of 7–185K. We drew the scattering-length density distribution as three dimensional graphic images and used the same isosurface level for all temperatures. The negative scattering length density, corresponding to the H atoms of CH4, was observed only in the large cage. The positive scattering length density attributed to the C atom of CH4 was observed at the center of each cage. With an increase in temperature, the negative and positive scattering length densities in the large cage disappear. The positive scattering length density remains at the center of the small cage regardless of temperature. These results strongly indicate that the motions of CH4 depend on the cage size and geometry. [Copyright &y& Elsevier]

Abstract: We measured neutron diffraction profiles of powdered KOD-doped D2O ice to investigate the formation and growth of ice XI, a deuterium-ordered phase of ice, from ice Ih, a disordered phase. During the measurements, the ice was annealed at 57K for about 17h, and then warmed up and kept at 68K for about 55h, which are below the transition temperature . The diffraction profiles for the doped ice at 57K did not change with time and were close to those for ice Ih with the deuterium-disordered arrangement. However, when the temperature increased from 57 to 68K, the diffraction profiles changed. We carried out the Rietveld analysis with the parameters for a two-phase model to obtain the structural evidence of the appearance and the growth of ice XI. The analysis provided evidence of ice XI as space group Cmc21 at 68K. The temporal increase of the mass fraction of ice XI showed that nucleation of ice XI began just after warming up to 68K. Then, ice XI grew for several days in the doped ice. This study provides first structural observations of the growth of ice XI. [Copyright &y& Elsevier]

Abstract: From neutron powder-diffraction experiments, we have studied the growth process of ferroelectric ice XI (eleven) with deuteron-ordered arrangements. We measured time-resolved neutron diffraction of 0.001-M KOD-doped D2O ice. We observed the growth of ice XI at 72–74K. The mass fraction f (the ratio of mass of ice XI to that of the doped ice) linearly increased with time for about 2 days. The de-transformed ice Ih, obtained after warming above the transition temperature of 76K, retransformed to ice XI at 66K. The observed increase of f with time is in good agreement with the nucleation process of the ordering and the constant growth of the ordered domain. A large fraction of ice Ih sample doped with sodium hydroxide changed to ice XI at 68K. The results suggest that large quantities of ice on cold icy bodies in our solar system are able to transform to ice XI, which may be detectable by space telescope and planetary exploration. [Copyright &y& Elsevier]

A stilbazolium material comprising 4-dimethylamino- N′-methyl-4′-stilbazolium tosylate (DAST), which has a large nonlinear optical susceptibility, was studied for application in terahertz (THz)-wave generation. The temperature-dependent structure of the DAST crystal was measured by using powder X-ray diffraction from −100 to 200 °C, indicating a volume expansion of 4.6 %. The lattice constants show anisotropic thermal expansion. Also, the temperature dependence of THz absorption spectra was measured by terahertz time-domain spectroscopy (THz-TDS) in the temperature range varying from −80 to 88.1 °C. A strong absorption peak was found at around 1 THz, shifting slightly toward a lower frequency with increasing temperature. The temperature dependence of the THz spectra was compared with that of X-ray diffraction. The shifting of THz-vibrational frequencies of the DAST crystal suggests that the change in its lattice structure is temperature dependent. [ABSTRACT FROM AUTHOR]

The refined crystal structure of stilbazolium derivatives was determined by neutron diffraction. The interatomic distances between the cation and the anion increased when the 4-position of the benzenesulfonate counteranion had a larger atom. The absorption coefficients of the 4-halobenzenesulfonate stilbazolium derivatives in the THz region became lower. [ABSTRACT FROM AUTHOR]

We report structural effect for Ni-doping in lithium cobalt oxide (LiCoO2) studied by the time-of-flight (TOF) neutron powder diffractions measured at RT. Crystal and local structures of LiCo1−xNixO2 (x=0, 0.2, 0.4, 0.6, 0.8, 1) powders, that were prepared by the solid-state reaction methods, have been respectively examined by using the IBARAKI Neutron Design Diffractometer (iMATERIA) of JPARC and Nanoscale-Ordered Material Diffractometer (NOMAD) of ORNL. The Rietveld refinement for neutron diffraction data of LiCo1−xNixO2 that all have been indexed to the rhombohedral system with trigonal symmetry in the space group R-3m, revealed the lattice parameter c/a ratio that tends to the ideal value as decreasing Ni-contents, while the atomic pair distribution function (PDF) analysis for neutron data of LiCo1-xNixO2 revealed that the Co–O and the Ni–O pair correlation lengths under the first peak of G(r) that respectively vary from 1.88 to 1.9Å and from 1.98 to 2.0Å, with average Ni–O correlation length (1.99Å) seems to be slightly larger than average Co–O correlation length (1.89Å). Rather than that resulted by the Rietveld analysis, the PDF analysis suggested that the diffusion pathways between Co–O in the LiCo1−xNixO2 system remain stable at ~1.89Å for all Ni-contents. [ABSTRACT FROM AUTHOR]

Abstract: We synthesized the intermetallic compound GdNi3, which has a PuNi3-type structure (space group R-3m), and investigated its P–C isotherm. The refined lattice parameters were a = 0.4993(1) nm and c = 2.4536(4) nm. In the first absorption process, two plateaus were observed, and the maximum hydrogen capacity reached 1.07 H/M. In the first desorption process, a narrow and sloping plateau was observed at approximately 0.02 MPa. After the first full desorption, 0.6 H/M of hydrogen remained in the sample. This sample showed severe peak broadening in the XRD pattern, indicating that the metal sublattice deformed from the original alloy. No plateau region was observed in the second absorption–desorption cycle. [Copyright &y& Elsevier]

Abstract: The crystal structure and hydrogenation properties of Ce2Ni7-type Gd2Ni7 were investigated by X-ray diffraction (XRD) and the hydrogen pressure–composition (P–C) isotherm. Ce2Ni7-type Gd2Ni7 was obtained by annealing at 1523 K for 12 h and quenching in ice water. Two superlattice reflections (002 and 004) of the Ce2Ni7-type were clearly observed at 2θ = 7.3° and 14.6° in the XRD profile. The refined lattice parameters were a = 0.49662(9) nm and c = 2.4255(3) nm, respectively. Two plateaus were clearly observed during the absorption–desorption process in the P–C isotherm. The first and second plateaus were at 0.015 and 0.13 MPa, respectively, in the first desorption. The maximum hydrogen capacity reached was 1.13 H/M. The enthalpy and entropy were calculated as −20 kJ/mol H2 and −80 J/mol H2 K, respectively, from the van’t Hoff plot. After the P–C isotherm, the GdNi5 cell expanded by 2.15%, but the Gd2Ni4 cell shrank by 2.83%. [Copyright &y& Elsevier]

We successfully synthesized the new intermetallic compound Gd5Ni19 and determined its crystal structure by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). The structure is a Sm5Co19-type superlattice structure (2H, space group P63/mmc), and the lattice parameters were determined as a = 0.4950(1) nm and c = 3.2161(5) nm by X-ray Rietveld refinement. The XRD results agreed with the STEM analysis results. The P-C isotherm of Gd5Ni19 was measured at 233 K. In the first absorption cycle, the maximum hydrogen capacity reached 1.07 H/M at 2.0 MPa. The sloping plateau was observed in the first absorption-desorption cycle. The maximum hydrogen capacity decreased by 0.87 H/M in the second absorption cycle, implying that hydrogen in the amount of H/M = 0.20 remained in the alloy before the second absorption-desorption cycle. [ABSTRACT FROM AUTHOR]

Abstract: Crystal structures of carbon dioxide deuterohydrate were studied by neutron powder diffraction at temperatures from 10 to 200K. Maps of scattering length density distribution were obtained using a maximum entropy method (MEM), which clarified the motion of CO2 molecules in the hydrate. In small cages, the carbon atom of the CO2 molecule is at the center of the cage, and the oxygen atoms of CO2 revolve freely around the carbon atom. In large cages, the carbon atom also is at the center of the cage, but the oxygen atoms tend to revolve around the carbon atom along the plane parallel to the hexagonal facets of the cage. [Copyright &y& Elsevier]

Abstract: In order to discuss oxide ion conduction mechanism for LaGaO3-based perovskite compounds, doping effects were investigated using two kinds of solid solutions whose oxygen vacancy concentrations are the same: one is La0.9Sr0.1Ga0.9Mg0.1O2.9 with A-site and B-site substitutions and the other is LaGa0.8Mg0.2O2.9 with only B-site substitution. Conductivity measurements showed that La0.9Sr0.1Ga0.9Mg0.1O2.9 had a circumstance whereby oxide ion could more easily diffuse in the perovskite structure than in LaGa0.8Mg0.2O2.9. Structural analyses using neutron diffraction found out the following three differences: the first finding was that the saddle point formed by two A-site cations and one B-site cation in La0.9Sr0.1Ga0.9Mg0.1O2.9 was larger than that in LaGa0.8Mg0.2O2.9 due to larger displacements of A-site and B-site cations; the second was that the doubly doping with Sr and Mg was more effective for reduction of GaO6 octahedral tilt angles than the doping with Mg; the last was that La0.9Sr0.1Ga0.9Mg0.1O2.9 had larger oxygen displacement than LaGa0.8Mg0.2O2.9. It was considered that these structurally related parameters dominated the high oxide ion conduction in LaGaO3-based perovskite compounds. [Copyright &y& Elsevier]

We report a series of layered superconductors, anti-ThCr2Si2-type RE2O2Bi (RE = rare earth), composed of electrically conductive Bi square nets and magnetic insulating RE2O2 layers. Superconductivity was induced by separating the Bi square nets as a result of excess oxygen incorporation, irrespective of the presence of magnetic ordering in RE2O2 layers. Intriguingly, the transition temperature of all RE2O2Bi including nonmagnetic Y2O2Bi was approximately scaled by unit cell tetragonality (c/a), implying a key role in the relative separation of the Bi square nets to induce superconductivity. [ABSTRACT FROM AUTHOR]

In this study, magnetization and neutron diffraction of anti-ThCr2Si2-type Tb2O2Bi polycrystals were measured at various temperatures. The magnetization cusp at 11.1 K was confirmed to correspond to antiferromagnetic ordering with a propagation vector of [0.5 0.5 0]. In addition, a metamagnetic behavior was observed below 5.0 K. The metamagnetic behavior could be attributed to the incommensurate magnetic structure with an anomaly at 5.0 K. [ABSTRACT FROM AUTHOR]

Abstract Maximum Entropy Method (MEM) is one of powerful tools for material science. We developed the program Z-MEM for evaluation of electron and nuclear density distribution by MEM analysis and Fourier synthesis. This code is designed by the multi-threading library OpenMP, so that the calculation performance is significantly improvements for MEM analysis. Z-MEM is bundled in Z-Rietveld , which is Rietveld software for X-ray and neutron powder diffraction, via the application programming interface (API). Since Z-MEM have equipped with the graphical user interface operations, users can perform from Rietveld refinement to MEM analysis seamlessly. [ABSTRACT FROM AUTHOR]

A new and promising P2-type layered oxide, Na5/6[Li1/4Mn3/4]O2 is prepared using a solid-state method. Detailed crystal structures of the sample are analyzed by synchrotron X-ray diffraction combined with high-resolution neutron diffraction. P2-type Na5/6[Li1/4Mn3/4]O2 consists of two MeO2 layers with partial in-plane √3 a × √3 a-type Li/Mn ordering. Na/Li ion-exchange in a molten salt results in a phase transition accompanied with glide of [Li1/4Mn3/4]O2 layers without the destruction of in-plane cation ordering. P2-type Na5/6[Li1/4Mn3/4]O2 translates into an O2-type layered structure with staking faults as the result of ion-exchange. Electrode performance of P2-type Na5/6[Li1/4Mn3/4]O2 and O2-type Li x[Li1/4Mn3/4]O2 is examined and compared in Na and Li cells, respectively. Both samples show large reversible capacity, ca. 200 mA h g−1, after charge to high voltage regardless of the difference in charge carriers. Structural analysis suggests that in-plane structural rearrangements, presumably associated with partial oxygen loss, occur in both samples after charge to a high-voltage region. Such structural activation process significantly influences electrode performance of the P2/O2-type phases, similar to O3-type Li2MnO3-based materials. Crystal structures, phase-transition mechanisms, and the possibility of the P2/O2-type phases as high-capacity and long-cycle-life electrode materials with the multi-functionality for both rechargeable Li/Na batteries are discussed in detail. [ABSTRACT FROM AUTHOR]

Abstract: Neutron diffraction studies were performed on the spinel oxide system Mg x Co1−x Cr x Fe2−x O4 (x =0.0, 0.25, 0.50, 0.75 and 1.0) as a function of temperature. Presence of magnetic long-range order at low temperatures was confirmed from the evolution of Bragg reflections with the decrease of temperature. Magnetic structural properties were determined from the Rietveld analysis of neutron diffraction data recorded in the temperature range 10–810K. Sublattice and net magnetic moments for various compositions at various temperatures were found out from the analysis. The transition temperatures were also determined for all the compositions. A decreasing ferrimagnetic order with increasing substitution was revealed from the decreasing ordered sublattice moments. Huge diffuse signals around the 111 Bragg diffraction line were observed in the neutron patterns of the composition x =1.0 below the Curie temperature indicating the existence of magnetic spin clusters. Hysteresis and low field dc magnetization measurements were done on the compositions x =0.75 and 1.0. Thermo-magnetic irreversibility in the zero-field cooled and field cooled magnetization together with a shallow transition below Curie temperature was also observed. The various observations suggest a canted ferrimagnetic ordering in the composition range x ≤0.75 and a semi-spin glass like behavior at x =1.0. A super-paramagnetic behavior below the paramagnetic state is also suggestive from the observed features. [Copyright &y& Elsevier]

Abstract: Quaternary spinel compound Mg x Co1−x Cr x Fe2−x O4 (x =0.0, 0.25, 0.50, 0.75 and 1.0) was synthesized in the solid state sintering method. Neutron powder diffraction measurements at room temperature were performed on the materials. Rietveld refinement of the neutron powder diffraction data was done for determining the cation distribution and crystallographic characterization of the system. The refinement yielded a mixed cationic distribution with Co, Fe and Mg being distributed over tetrahedral and octahedral sites in varying proportions while Cr was found to uniquely occupy the octahedral interstices. Increase of tetrahedral bond distance and decrease of octahedral bond distance with x was also revealed from the refinement. Sublattice and net magnetic moments at room temperature were also deduced from the refinement of room temperature neutron diffraction data. [Copyright &y& Elsevier]

Abstract: A layered perovskite compound with Na+, D3O+ ions (H3O+) and D2O molecules (H2O) in the interlayer, D x Na1− x LaTiO4·yD2O, has been prepared by an ion-exchange/intercalation reaction with dilute DCl solution, using an Ruddlesden–Popper phase, NaLaTiO4. Its structure has been analyzed in order to clarify the interlayer structure by Rietveld method, using powder neutron diffraction data. The structure analysis revealed that the layered structure changed from the space group P4/nmm–I4/mmm after the ion-exchange/intercalation reaction, and it induced the transformation of perovskite layers from staggered to an eclipsed configuration. The D2O molecules and D3O+ ions loaded in the interlayer statistically occupied the sites around a body center position of rectangular space surrounded by eight apical O atoms of TiO6 octahedra in upper and lower layers. [Copyright &y& Elsevier]

Abstract: A deuterated n=1 Ruddlesden–Popper compound, DLnTiO4 (HLnTiO4, Ln=La, Nd and Y), was prepared by an ion-exchange reaction of Na+ ions in NaLnTiO4 with D+ ions, and its structure was analyzed by Rietveld method using powder neutron diffraction data. The structure analyses showed that DLaTiO4 and DNdTiO4 crystallized in the space group with a=3.7232(1) and c=12.3088(1)Å, and a=3.7039(1) and c=12.0883(1)Å, respectively. On the other hand, DYTiO4 crystallized in the space group with a=11.460(1), b=5.2920(4), c=5.3628(5)Å and β=90.441(9)°. The loaded protons were found to statistically occupy the sites around an apical oxygen of TiO6 octahedron in the interlayer of these compounds, rather than Na atom sites in NaLnTiO4. [Copyright &y& Elsevier]

Abstract: A protonated n =1 Ruddlesden–Popper compound, HLaTiO4 (DLaTiO4), has been prepared by an ion-exchange reaction of Na+ ions in NaLaTiO4 with H+ (D+) ions, and its structure has been analyzed in order to clarify the location of protons in the interlayer space, using powder neutron diffraction data. The crystal structure of DLaTiO4 belongs to the same space group, P4/nmm, as that of parent NaLaTiO4, and the D atoms were found to statistically occupy eight equivalent sites around an apical O atom of a TiO6 octahedron in the interlayer, which are different from the Na atom sites in NaLaTiO4. A comparison between DLaTiO4 and NaLaTiO4 indicated that the protonation brought the shrinkage of the interlayer space and the distortion of the TiO6 octahedron. [Copyright &y& Elsevier]

Abstract: Structural characteristics of Fe-doped LaGaO3-δ were studied by differential scanning calorimeter, neutron and high-temperature X-ray powder diffraction measurements. It was found that a phase transition temperature increases in proportion to an amount of Fe. The crystal structure could be described as a low-temperature orthorhombic phase (Pnma) and a high-temperature rhombohedral one (), respectively. Lattice parameters and bond lengths between M (=Ga/Fe) and O are monotonically expand with increasing Fe-content on both orthorhombic and rhombohedral phases. This means that a substitution of Ga3+ with Fe3+ leads to an electronic configuration of t2g3eg2 (high-spin state, HS). [Copyright &y& Elsevier]

Defect structures of the lanthanum-substituted PbWO4 prepared by mechanical alloying (MA) were investigated by means of powder neutron diffraction and FT-IR, to compare with that of the oxide ion conductive sintered samples. Neutron diffraction revealed that Pb1-xLaxWO4+x/2 prepared by MA possessed the lead site deficiency in the lattice. In addition, it was also found that occupation factors of the lead site were still smaller than the nominal value even for the mechanically alloyed Pb1-xLa2x/3WO4. The vacancy formation at the lead site of the mechanically alloyed Pb1-xLaxWO4+x/2 was also corroborated from the splitting of the absorption band around 800 cm-1 ascribed to the W–O stretching vibration of WO4 tetrahedron. At the end of this paper, the formation process of the lead site vacancy was discussed in the sintered Pb1-xLaxWO4+x/2 during milling. [Copyright &y& Elsevier]

The crystal structure of sintered β-tricalcium phosphate, Ca3(PO4)2, was refined using a high-resolution neutron powder diffraction data and the Rietveld method. This material was confirmed to have a rhombohedral structure (space group R3c, Z=21). Unit-cell parameters with higher precision (a=b=10.4352(2) A˚, c=37.4029(5) A˚, α=β=90°, and γ=120° in the hexagonal setting) and positional parameters for oxygen with equal precision were obtained by the neutron powder diffraction technique, compared with the single-crystal X-ray diffraction data by Dickens et al. (J. Solid State Chem. 10 (1974) 232). The site Ca(4) with atomic coordinates [0.0, 0.0, −0.0851(6)] was confirmed to be very different from the other four Ca sites: The position Ca(4) is three-fold coordinated with oxygen atoms, and has lower occupancy factor of 0.43(4), and a higher isotropic thermal parameter. On the contrary, each of the Ca(1), Ca(2), Ca(3), and Ca(5) is fully occupied by one Ca atom and these positions are coordinated with seven, eight, eight, and six oxygen atoms, respectively. The bond valence sums of Ca(4) and Ca(5) are lower (0.7) and higher (2.7), respectively, than the others (1.8–2.1). [Copyright &y& Elsevier]

High-temperature phase transition of lanthanum niobium titanate La0.64(Ti0.92,Nb0.08)O3 has been studied using neutron powder diffraction and the Rietveld method. The material is orthorhombic (Cmmm) between 295 and 534 K, while it is tetragonal (P4/mmm) between 637 and 740 K. The anti-phase tilt along the b axis of the oxygen octahedron around Ti and Nb atoms was found to induce the tetragonal-to-orthorhombic phase transition. The angle of the tilt and the b/a ratio of cell parameters decrease with an increase of temperature and become 0° and unity, respectively, at a transition temperature between 534 and 637 K. [Copyright &y& Elsevier]

Abstract: Temperature-dependent neutron diffraction studies were done on the spinel oxide system Mg x Co1− x Cr x Fe2− x O4 (x=0.0, 0.25, 0.50, 0.75 and 1.0). Neutron diffraction data recorded in the temperature range 10–810K were analyzed in the Rietveld method. Ordered sublattice magnetic moments of the five compositions of the spinel series at various temperatures were deduced from the analysis. A decreasing ordered moment with increasing substitution (x) was found indicating a gradual weakening of ferrimagnetic order. Huge diffuse signals around the 111 Bragg diffraction peak were found in the neutron patterns of the composition x=1.0 below the Curie temperature manifesting a build-up of short-range magnetic spin clusters. The observed features suggest a canted ferrimagnetic structure in the composition range x⩽0.75 and a semi-spin glass-like transition at x=1.0. [Copyright &y& Elsevier]

NdBaInO4 is obtained from a 1:1:1 molar mixture of BaCO3, In2O3, and Nd2O3 by calcination (1000 °C, 8 h) and sintering (air, 1400 °C, 24 h). [ABSTRACT FROM AUTHOR]