Shigeho Sueno

Single Crystal X-Ray Structure Analysis of Bi2(Sr, Ca)2CuOx and Bi2(Sr, Ca)3Cu2Ox Superconductors

Average crystal structures of Bi2(Sr, Ca)2CuOx and Bi2(Sr, Ca)3Cu2Ox were analyzed using single crystal X-ray intensity data applying anisotropic temperature factors. Crystal data: Bi2Sr1.60Ca0.40CuO6, Bbmb, a=5.3826(8) A, b=5.3761(11), c=24.384(7), Rw=0.108 for 282 reflections; Bi2.06Sr1.70Ca1.24Cu2O8, Bbmb, a=5.3946(8), b=5.3895(13), c=30.649(12), Rw=0.064 for 354 reflections. Precession photographs show that Bi2Sr1.60Ca0.40CuO6 has a monoclinic modulated structure and Bi2.06Sr1.70Ca1.24Cu2O8 has an orthorombic one. The incommensurate modulated structures were qualitatively illustrated by using a modulation wave model.

Trace element partitioning between silicate perovskites and ultracalcic melt

Abstract Determination of partition coefficients for Mg- and Ca-perovskite/melt has been performed for 27 trace elements by combination of high pressure–temperature experiments using a multi-anvil apparatus and in situ trace element analysis by secondary ion mass spectrometry (SIMS). Each of the crystallographic sites for the perovskites gives rise to a parabola-shaped peak on the partition coefficient versus ionic radius diagram. This suggests that the elemental partitioning is governed by the structural control even under the lower mantle condition. On the diagrams for Mg- and Ca-perovskites, sharpness and peak position of peaks are consistent with geometrical flexibility of the corresponding coordination polyhedra. The relative height between the partition curves for homovalent ions is controlled by electrostatic charge balancing among their crystallographic sites. Large partition coefficients of Th and U in Ca-perovskite suggest that these elements play an important role for the heat source in the Earth’s lower mantle.

Oxygen isotope evidence regarding the formation of spinel-bearing chondrules

Oxygen isotope compositions of individual mineral grains in two spinel-bearing chondrules have been determined by secondary ion mass spectrometry. O isotope ratios of spinel grains in a plagioclase-rich chondrule were extremely 16 O-rich (d 18 O d 17 O 35‰) indicating close relationship to spinels in Ca‐Al-rich inclusions (CAIs), whereas O isotope ratios of a spinel grain in barred-olivine chondrule were less enriched in 16 O( d 18 O d 17 O 10‰). The degree of 16 O-excesses among minerals within each chondrule was parallel to the crystallization sequences. These measurements suggest that some CAI-spinel grains were incorporated into the chondrule precursors, and that the O isotopic variation among minerals may result in incomplete exchange of O isotopes between 16 O-rich chondrule melt and 16 O-poor ambient nebular gas. The mesostasis having an O-isotopic composition near the terrestrial fractionation line may have been somewhat affected by the aqueous alteration in the parent body.

Hydrogen analysis in quartz crystals and quartz glasses by secondary ion mass spectrometry

Abstract Microanalysis of hydrogen in quartz crystals and quartz glasses has been developed by secondary ion mass spectrometry (SIMS). The secondary ion intensities of hydrogen are proportional to the hydrogen contents determined by infrared (IR) absorption over the range of 5 to 3000 ppma H/Si. The correlation between SIMS and IR results indicates that secondary ion yields of hydrogen are independent of crystal structure. This SIMS method could reveal correlations between hydrogen distribution and hydrolytic weakening at the microscopic level.

Preparation and Properties of Single Crystals of the High-Tc Oxide Superconductor in the Bi-Sr-Ca-Cu-O System

Single crystals of the superconductor in the Bi-Sr-Ca-Cu-O system were prepared by the Bridgman method. Platy crystals annealed at various physical conditions were examined by electrical resistivity measurements and single crystal X-ray diffraction studies. The superconducting transition temperature (Tc) depended on the annealing temperatures and oxygen pressure. Corresponding to annealing conditions, single crystal X-ray diffraction patterns on (hk1)* Layer precession photographs systematically changed at room temperature. This may be related to the slight differences of the cell parameters of each specimen.

Geochemical properties of lithospheric mantle beneath the Sino-Korea craton; evidence from garnet xenocrysts and diamond inclusions

Abstract Composition of the lithospheric mantle beneath the Sino-Korea craton is investigated, using garnet xenocrysts, mantle xenoliths in kimberlites and mineral inclusions within diamonds. It is verified that the lithospheric mantle beneath the Sino-Korea craton is mainly composed of strongly depleted garnet lherzolite and garnet harzburgite, with a very small proportion of eclogite. The Mg number of peridotite olivine ranges from 91.5 to 95.0, with a peak at about 92.5. Estimated Mg/Si ratio ranges from 1.26 to 1.31. Differences of the Sino-Korea cratonic peridotite with the upper mantle in oceanic and off-cratonic regions are significant. Combined with seismic information, we propose that this compositional anomaly of Archean lithospheric mantle is a worldwide phenomenon. Evident differences in chemical composition, thickness and temperature of the present lithosphere in the Sino-Korea craton region with that established in this study show that the extremely refractory lithospheric mantle was replaced by convective mantle after the kimberlite eruption. It seems to be the first locality that detachment of cratonic lithospheric mantle was verified.

X-Ray Single Crystal Structure Analysis of Tetragonal Ba2YCu3-xO7-y, a High Temperature Form of the Superconductor

Crystal data: tetragonal, space group P4/mmm, a=3.8640(4), c=11.755(3) A, final R factor=0.036 for 161 independent observed reflections. Cu1 and two O1 form linear O-Cu-O dumbell (Cu-O1 1.808 A) with additional square planer O2 group (site occupancy=0.2) around Cu1. Cu2 is in square pyramidal coordination of oxygen composed of square-planer O3 group (Cu-O3 1.944 A) and an apical O1 (Cu-O1 2.434 A). The Y and Ba are in ordered arrangement along the c axis. This tetragonal phase is a high temperature form of the orthorhombic phase and the transition is related with ordering of the oxygen vacancy. Presence of strong metal-metal interactions were presumed because there exist Ba-Ba, Ba-Y and Ba-Cu distances significantly shorter than sum of their corresponding metallic radii.

Crystal structure of Ba2YCu3−xO7−y, a superconductive compound determined by X-ray single crystal diffraction method

Abstract Crystal structure of Ba2YCu3−xO7−y was determined and refined based on the X-ray single crystal diffraction data. Its space group is either pseudo-tetragonal (Pmmm) or tetragonal (P4/mmm) with cell dimensions a-, b-axis = 3.87 A and c = 11.715 A . The structure is built up of perovskite-like [Ba2Cu3−xO7−y] layers connected by Y atoms, where x = 0.12, y = 1.39 for Pmmm model and x = 0.11, y = 0.34 for P4/mmm. Final residual R (unweighted) is 0.051 for the former and 0.039 for the latter.

Single-Crystal X-Ray and Magnetization Study of the 106 K Bi–Sr–Ca–Cu–O Superconductor

Single crystals of Bi2(Sr, Ca)4Cu3Ox were studied by an X-ray precession camera together with the 232 and 221 phases. The 243 crystals were selected from two types of the specimens: (1) quenched from 810°C (Tc=80 K) and (2) annealed subsequently at 500°C for 4 hours (Tc=106 K). X-ray photographs revealed that the 243 phase has basically a 37 A stacking unit along the c-axis with a remarkable stacking disorder. The direction of the modulation is not parallel to the b*-axis but inclined 35.7° from the b*-axis for the 243 phase. SQUID study revealed that the volume fraction of the 106 K phase at 50 K was about 57%.

A 105 K superconducting phase in the Bi-Sr-Ca-Cu-O system

We report a 105 K superconducting phase crystallized at 883°C as a major phase with large grain sizes. X-ray powder diffraction showed a very broad 002 reflection of 17.8 A, although chemical compositions were relatively homogeneous. The 105 K phase has a Cu-rich and Bi-poor composition compared with the 80 K superconducting phase.