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In the present work, iron–sillenite (Bi25FeO40) was synthesized using a simple solid-state reaction method and characterized. The effects of the synthesis conditions on the phase purity of Bi2O3/Fe3O4, morphological features, and possible application as an XRD/MRI dual-contrast agent were investigated. For the synthesis, the stoichiometric amounts of Bi2O3 and Fe3O4 were mixed and subsequently milled in a planetary ball mill for 10 min with a speed of 300 rpm. The milled mixture was calcined at various temperatures (550 ° C, 700 ° C, 750 ° C, 800 ° C, and 850 ° C) for 1 h in air at a heating rate of 5 °C/min. For phase identification, powder X-ray diffraction (XRD) analysis was performed and infrared (FTIR) spectra were recorded. The surface morphology of synthesized samples was studied by field-emission scanning electron microscopy (FE-SEM). For the radiopacity measurements, iron–sillenite specimens were synthesized at different temperatures and mixed with different amounts of BaSO4 and Laponite solution. It was demonstrated that iron–sillenite Bi25FeO40 possessed sufficient radiopacity and could be a potential candidate to meet the requirements of its application as an XRD/MRI dual-contrast agent. [ABSTRACT FROM AUTHOR]

A phase with the Cu[O.sub.2] planes separated by a 12 Angstrom thick quadruple-fluorite-layer block can be synthesized in a single phase and strongly oxygenated form to display superconductivity with a [T.sub.c] value as homologous series. The results have shown that [T.sub.c] has remained unaffected upon inserting additional fluorite-structured layers between the two Cu[O.sub.2] planes as long as the hole-doping level of the planes is kept constant.

X-ray absorption near-edge structure spectroscopy is utilized as a probe to examine the hole states of phases of the homologous series of (Cu,Mo)-12s2, for which the member phases differ from each other by the number (s) of cation layers in the fluorite-structured (Ce,Y)-[[[O.sub.2]-(Ce,Y)].sub.s-1] block between the Cu[O.sub.2] planes. The [T.sub.c] value of superconductive copper oxides is found not to depend on the distance between two adjacent Cu[O.sub.2] planes as long as the hole-doping level and the immediate (crystal) chemical surroundings of the planes are kept the same.

Among high-Tc superconductive copper oxides, there have been known phases that contain fluorite-structured layers as an additional "blocking block" between adjacent CuO2 planes. Here, we report that even a phase with the CuO2 planes separated by a 12-Å thick quadruple-fluorite-layer block can be synthesized in a single phase and strongly oxygenated form to exhibit superconductivity with a Tc value as high as 55 K. The new phase is the fourth member of the (Cu,Mo)Sr2(Ce,Y)5Cu2O5+2s+δ or (Cu,Mo)-12s2 homologous series. Comparison with the previously known s = 1, 2, and 3 members of the series reveals the amazing conclusion that Tc remains essentially unaffected upon inserting additional fluorite-structured layers between the two CuO2 planes as long as the hole-doping level of the planes is kept constant. [ABSTRACT FROM AUTHOR]

The compounds BiMO2NO3, with M=Pb, Ca, Sr, and Ba, were obtained as single-phase products from solid-state reactions in an atmosphere of nitrous gases. The oxide nitrates with Pb and Ca crystallize in the tetragonal space group I4/mmm with two formula units per unit cell; the oxide nitrates with Sr and Ba crystallize in the orthorhombic space group Cmmm with four formula units per unit cell. Lattice parameters at room temperature are a=397.199(4), c=1482.57(2) pm for M=Pb; a=396.337(5), c=1412.83(3) pm for M=Ca; a=1448.76(3), b=567.62(1), c=582.40(1) pm for M=Sr and a=1536.50(8), b=571.67(3), c=597.55(3) pm for M=Ba. The structures, which were refined by powder X-ray diffraction, consist of alternating [BiMO2]+ and [NO3]- layers stacked along the direction of the long axis. IR and thermogravimetric data are also given. The various M2+ cations in BiMO2NO3 are compatible with each other; therefore and because of their layer-type structure, these compounds are interesting precursors for oxide materials, e.g., the HTSC compounds (Bi,Pb)2Sr2Can-1CunOx. [Copyright &y& Elsevier]