Since the effective focal size of synchrotron beam source is smaller than laboratory x-ray source, it is expected that evaluation of crystallite size by analysis of particle statistics in powder diffractometry has sensitivity in the region smaller than several micrometers. In this presentation, we report the results to examine this prediction, based on the data collected on the powder diffraction beam line BL-4B2 at KEK-PF in Tsukuba.

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Crystal structure and structural disorder of Ba₃MgSi₂O₈ were reinvestigated by laboratory X-ray powder diffraction. The title compound was found to be trigonal with space group P-3m1, Z = 1, unit-cell dimensions a = 0.561453(4) nm, c = 0.727629(4) nm and V = 0.198641(2) nm³. The initial structural model used for structure refinement was taken from that of glaserite (K₃NaS₂O₈) and modified by a split-atom model. In the split-atom model, one of the two types of Ba sites and SiO₄ tetrahedra were, respectively, positionally and orientationally disordered. The new crystal structure and structural disorder were refined by the Rietveld method. The maximum-entropy methods-based pattern fitting (MPF) method was used to confirm the validity of the split-atom model. The final reliability indices calculated from MPF were R_wp = 6.52%, S = 1.36, R_p = 4.84%, R_B = 0.97% and R_F = 0.52%. Details of the disorder structure of Ba₃MgSi₂O₈ are shown in the 3D and 2D electron-density distribution maps determined by MPF.

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A new layered carbide, [Zr_0.72(3)Y_0.28(3)]Al₄C₄, has been synthesized and characterized by X-ray powder diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy (EDX). The atom ratios [Zr : Y] were determined by EDX, and the initial structure model was derived by the direct methods, and further refined by the Rietveld method. The crystal is trigonal (space group P-3m1, Z = 1) with lattice dimensions of a = 0.333990(5) nm, c = 1.09942(1) nm and V = 0.106209(2) nm³. This compound shows an intergrowth structure with [Zr_0.72Y_0.28C₂] thin slabs separated by Al₄C₃-type [Al₄C₄] layers. It is a new member with l = 1 and m = 1 of the homologous series, the general formula of which is (MC)_l(T₄C₃)_m (l = 1, 2 and 3, m = 1 and 2, (M=Zr, Y and Hf, T=Al, Si and Ge).

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Lanthane silicates with an apatite type structure have been expected for new solid electrolyte material for IT-SOFC because of their good conductivity at low temperature. In this study composite cathodes were prepared with the lanthane silicates and LSM. Their cathodic performances were examined and compared with that of the LSM-YSZ cathode. It was deduced that the cathodic performance of the composite depends not only on the conductivity but also a sinterability of the electrolyte materials used for the composite cathode.

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The Fabrication of Patterned and Ordered Ceramic Microstructures From Precursors by Pyrolysis

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In recent years, (100)-oriented cerium oxide (CeO₂) films have attracted increasing attention as catalysts because of the particular CeO₂ ability to store and release oxygen and the inherent high reactivity of the (100) plane. In this study, (100)-oriented CeO₂ films were prepared on amorphous glass substrates in a cold-wall type laser chemical vapor deposition (LCVD) apparatus using Ce(dpm)₄ as the precursor. The semiconductor laser (808 nm wavelength) system employed in this study allowed a maximum power output (PL) of 200 W and a defocused laser spot about 20 mm in diameter. CeO₂ films prepared at PL=0 and 200 W were non-oriented. However, at PL=50, 100 and 150 W, CeO₂ films exhibited a (100) preferred orientation and a feather-like columnar microstructure. Particularly, the CeO₂ films prepared at PL=100 W showed the almost complete (100) orientation and the highest deposition rate of about 120 umh^-1.

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YBa₂Cu₃O_7-x (YBCO) films were prepared by laser chemical vapor deposition (LCVD) using Y(DPM)₃, Ba(DPM)₂ / Ba(TMOD)₂ and Cu(DPM)₂ as the precursors. A continuous wave Nd:YAG laser with a high power output of 200 W was employed, and a large laser spot of 20 mm in diameter was irradiated on Al₂O₃ substrate. YBCO films in a single phase were obtained. The YBCO films had an appreciable c-axis orientation, consisting of rectangular grains about 30 um in size. The highest deposition rate was 100 um / h, which was much higher than that of deposited by MOCVD (usually 0.1-1 um / h).

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Zinc oxide powders were synthesized by liquid-phase method at low temperature. Zinc acetate was used as zinc source materials. Hexamethylenetetramine was used as a precipitant. Ethylene glycol and water were employed as solvents. The reaction time was 12 h. Spherical ZnO particles were successfully obtained at 95ºC with 95vol% of ethylene glycol and 5vol% of water as solvents.

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Blanket-like ZnO nanowhisker assemblies were fabricated using a freestanding ZnO nanoparticles layer by an aqueous solution deposition. X-ray diffraction and field emission scanning electron microscopy clarified the crystalline phase, orientation, morphology, and microstructure. Thermal treatment of the zinc acetate dihydrate layer resulted in the formation and delamination of the ZnO nanoparticles layer on the glass substrate. The growth habits of ZnO crystals resulted in the growth of ZnO nanowhiskers preferentially orientated along the direction of the c-axis on the whole surface of the freestanding ZnO nanoparticles layer by heterogeneonous nucleation and growth. The hierarchical-structured blanket-like ZnO nanowhisker assemblies can be utilized for dye-sensitive solar cells and gas sensors because of their high surface-to-volume ratio.

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Recently, various ZnO nanostructures, such as nanowires, nanorod, and nanosheet have been investigated in solar cells and bio-sensors. In such applications, a high porosity and large surface area are required to improve the efficiency and activity. Therefore, two kinds of different ZnO nanostructures, nanotubes and nanoflowers were synthesized by an aqueous solution approach. Meanwhile, the performance of these devices depends critically on the adsorption properties of dye on ZnO nanostructures. In the present study, the adsorption properties of cytochrome c were investigated by UV-visible spectra. It was found that the adsorption of cytochrome c were strongly dependent on the crystalline structure and morphology of ZnO, and highly ordered nanotubes and nanoflowers show higher cytochrome c adsorption ability compared to that of nanorod arrays. The possible reason was the unique structure and large surface area of these two nanostructures.

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Alternative lead-free piezoelectric ceramics, in place of PbZrTiO3 (PZT)1-3) has been investigated, because it evoked problems of human health and environment. Thus, this development has attracted great deals of attention in material sciences. In the present study, we have succeded in the preparation of Bi0.5Na0.5TiO3 (BNT) and (NaK)NbO3 nanoparticles with narrow size distributions by the Gel-Sol method. Effects of the reaction condition on the size and morphology of the resulting particles will be discussed.

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X-ray fluorescence holography (XFH) provides three dimensional atomic images around specified elements. The XFH uses atoms as a wave source or monitor of interference field within a crystal sample, and therefore it can record both intensity and phase of scattered X-rays. Its current performance makes it possible to apply to ultra thin film, impurity and quasicrystal. In this paper, I show the theory including solutions for twin image problem, advanced measuring system, data processing for reconstruction of the atomic images and for obtaining accurate atomic positions, applications using resonant X-ray scattering and X-ray excited optical luminescence, and an example of XFH result on the local structure around copper in silicon steal.

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Our society needs semiconductor crystals in the fields of information, environment and energy. Silicon crystals are used for photo voltaic and large scale integrated circuits (LSIs) in the fields of energy and information, respectively. Concerning compound semiconductors, GaAs and InP are utilized in the field of information, and nitrides are for optical area. This paper focuses on melt growth, physical vapor transport and liquid phase epitaxy from the point of views of both numerical and experimental approach.

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A novel method to evaluate the mechanical property of a thin film on a substrate is developed, in which nanoindentation with a point-sharp indenter is utilized. Numerical analysis on indentation behavior is carried out with the finite element method to derive the indentation parameters of a film from the indentation behavior, which is not affected by the deformation of a substrate. Using the indentation parameters, the mechanical properties, such as Young's modulus, yield strength and Meyer hardness, of the film can be evaluated.

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