Ryoji Kiyanagi

Encapsulating Mobile Proton Carriers into Structural Defects in Coordination Polymer Crystals: High Anhydrous Proton Conduction and Fuel Cell Application

We describe the encapsulation of mobile proton carriers into defect sites in nonporous coordination polymers (CPs). The proton carriers were encapsulated with high mobility and provided high proton conductivity at 150 °C under anhydrous conditions. The high proton conductivity and nonporous nature of the CP allowed its application as an electrolyte in a fuel cell. The defects and mobile proton carriers were investigated using solid-state NMR, XAFS, XRD, and ICP-AES/EA. On the basis of these analyses, we concluded that the defect sites provide space for mobile uncoordinated H3PO4, H2PO4(-), and H2O. These mobile carriers play a key role in expanding the proton-hopping path and promoting the mobility of protons in the coordination framework, leading to high proton conductivity and fuel cell power generation.

Structural and Magnetic Phase Determination of (1-x)BiFeO3–xBaTiO3 Solid Solution

Solid solutions of (1- x )BiFeO 3 – x BaTiO 3 ( x = 0.0–1.0) were studied by the combination of X-ray and neutron powder diffraction methods in order to investigate structural and magnetic properties over a wide temperature region. The structure analyses revealed that there exists a hexagonal phase over the wide range of x , and a coexistence of a cubic or a tetragonal phase was revealed. The compositions of the two coexisting phases differ from each other, and Ba and Ti were found to favor the cubic or tetragonal phase. As x increases, the relaxation of the rhombohedral distortion in the hexagonal phase was observed. The decreases of the ferroelectric and the antiferromagnetic phase transition temperatures were also observed leading the suppression of the polarization and the magnetic moment of Fe 3+ ion at room temperature. As a whole, the ferroelectricity and ferromagnetism in this material were considered to arise from the remaining hexagonal phase.

Current status of a time-of-flight single crystal neutron diffractometer SENJU at J-PARC

SENJU is a state-of-the-art single crystal time-of-flight Laue diffractometer in Materials and Life Science Experimental Facility at Japan Proton Accelerator Research Complex (J-PARC). The diffractometer is designed for precise crystal and magnetic structure analyses under multiple extreme conditions, such as low temperature, high-pressure, high-magnetic field. Measurements using small sample less than 1.0 mm3 will be also realized, which allows us to study wide variety of materials. SENJU is using a poisoned decoupled moderator to obtain peak profiles of Bragg reflection, and intensity distributions of superlattice reflections and diffuse scatterings with good accuracy. At the beginning, the diffractometer will have 31 two-dimensional scintillator detectors to cover wide area of reciprocal lattice space by a single measurement. The instrument is currently under construction and is scheduled to start on-beam commissioning in February 2012.

SENJU: a new time-of-flight single-crystal neutron diffractometer at J-PARC

SENJU, a time-of-flight Laue-type single-crystal neutron diffractometer, was developed at the Materials and Life Science Experimental Facility of the Japan Accelerator Research Complex (J-PARC). Molecular structure analysis of a sub-millimetre taurine crystal and magnetic structure analysis of an MnF2 crystal were performed to evaluate its performance.

Time-of-Flight Three Dimensional Neutron Diffraction in Transmission Mode for Mapping Crystal Grain Structures

The physical properties of polycrystalline materials depend on their microstructure, which is the nano- to centimeter scale arrangement of phases and defects in their interior. Such microstructure depends on the shape, crystallographic phase and orientation, and interfacing of the grains constituting the material. This article presents a new non-destructive 3D technique to study centimeter-sized bulk samples with a spatial resolution of hundred micrometers: time-of-flight three-dimensional neutron diffraction (ToF 3DND). Compared to existing analogous X-ray diffraction techniques, ToF 3DND enables studies of samples that can be both larger in size and made of heavier elements. Moreover, ToF 3DND facilitates the use of complicated sample environments. The basic ToF 3DND setup, utilizing an imaging detector with high spatial and temporal resolution, can easily be implemented at a time-of-flight neutron beamline. The technique was developed and tested with data collected at the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Complex (J-PARC) for an iron sample. We successfully reconstructed the shape of 108 grains and developed an indexing procedure. The reconstruction algorithms have been validated by reconstructing two stacked Co-Ni-Ga single crystals, and by comparison with a grain map obtained by post-mortem electron backscatter diffraction (EBSD).

Indication of Tunneling State of Hydrogen Atom in Hydrogen-Bonded Material 5-Bromo-9-hydroxyphenalenon Studied by X-ray and Neutron Diffractions

The dielectric material with an isolated hydrogen-bond, 5-bromo-9-hydroxyphenalenon, was studied by means of neutron and X-ray diffractions in the temperature range between 300 and 10 K. Analyses on nuclear and electron density distributions revealed a discrepancy between the two distributions of the hydrogen atom in the hydrogen-bond region, leading to a local electronic dipole moment . Both a least-square structure analysis and the density distribution analysis by the maximum entropy method confirmed that the hydrogen atom occupies two equivalent sites near the center of the hydrogen-bond through the whole temperature range, even at the lowest temperature measured, 10 K. This feature, together with previous results on calorimetric, incoherent neutron scattering and far-infrared spectrum measurements, concludes that the hydrogen atom in the hydrogen-bond is in a tunneling state over the two sites. Consequently, 5-bromo-9-hydroxyphenalenon was experimentally identified as a quantum paraelectric material.

Investigation of the Structure of Single Crystal Sr3Ru2O7 by Neutron and Convergent Beam Electron Diffractions

The structure of Sr 3 Ru 2 O 7 was reinvestigated by a neutron diffraction and a convergent-beam electron diffraction (CBED) experiment on single crystals. The CBED experiment revealed that the space group of Sr 3 Ru 2 O 7 is Bbcb with an orthorhombic lattice with nanometer-size twin components in the crystal. Taking these observations into account, a structure analysis was carried out with the neutron data. It was found that RuO 6 -octahedrons connected each other have rotated about c -axis in the opposite direction. This result is consistent with the previous report by a powder neutron diffraction experiment.

Hydrogen-Bond Nature Studied by X-ray and Neutron Structure Analyses of MeHPLN at Room Temperature

The hydrogen-bonded material, 5-methyl-9-hydroxyphenalenon (MeHPLN), was studied by X-ray and neutron diffraction experiments at room temperature in order to understand the hydrogen-bond nature and the relation between the hydrogen-bonds and phase transitions. We found that there are obvious discrepancies between the positions of the hydrogen atoms obtained by the X-ray data and the ones obtained by the neutron data. This result indicates that the centers of the electron cloud of the hydrogen atoms are off from the nuclear positions. The discrepancy is markedly seen in the hydrogen atoms participating in the hydrogen-bonds. That is, there are local electronic dipolemoments in the hydrogen-bond region.

Instrument Design and Performance Evaluation of a New Single Crystal Neutron Diffractometer SENJU at J-PARC

A new single crystal time-of-flight neutron diffractometer has been installed at BL18 of the Materials and Life Science Experimental Facility of J-PARC. The diffractometer “SENJU” was designed for precise crystal and magnetic structure analyses using a small crystal less than 1 mm under multiple extreme environments such as low-temperature and high-magnetic field [1]. The first neutron beam was delivered to the sample position on March 5, 2012. Subsequently, the hardware and software of SENJU have been checked and confirmed that they worked fine. At the same time, diffraction experiments of several organic and inorganic crystals have been done using NaCl, 12CaO!7Al2O3 (Fig. 1), and so on. In these measurements, Bragg reflections in the high-Q region (d-spacing < 0.5 A) were clearly observed and analyzed successfully. In this presentation, we will show the instrument design and performance evaluation of SENJU in detail.

Single Crystal Neutron Diffraction Study of High Neutron Absorbing Compound EuGa4

Single crystal neutron diffraction measurement of EuGa4 has been carried out using time-of-flight single crystal neutron diffractometer SENJU at BL18 in MLF/J-PARC. In spite of extremely high neutron absorption of natural Eu (not enriched by Eu isotope), significant numbers of Bragg reflection were observed. Lattice parameters and lattice symmetry above TN (= 15 K) obtained from the positions and systematic extinction of the reflections were well agreed with the predefined results of single crystal X-ray diffraction. Furthermore, magnetic reflections were clearly observed below TN at positions of h+k+l = odd. Thus, antiferromagnetic structure of EuGa4 can be described with a propagation vector q = (0 0 0), which breaks a body-centered symmetry