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Semiconducting samples of a Bi-Ca-Sr-Cu oxide, having a nominal composition 4:3:3:4, were prepared by melting high purity oxides of the various elements. Superconducting samples were obtained by annealing the semiconducting samples at a temperature close to the melting temperature. Electrical resistivity measurements indicated the presence of two superconducting phases, one with the onset temperature at about 110 K, the other with a significantly lower onset temperature. The presence of this second phase is proven by the X-ray powder diffraction patterns. The crystalline structure of both the semiconductor and superconductor samples have almost equal lattice parameters, are orthorhombic but belong to different space groups: Fmmm and Bbmm, respectively. Following the hypothesis of some authors, this change in the symmetry seems due to the different position of Bi and O atoms in their plane. The electronic structure, shown by the f4 XPS, and L(III) XANES spectra of Bi indicate different coordinations of this element with the neighbouring atoms of oxygen for superconducting and semiconducting samples.

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Authors: GIARDINA M D, JRC Ispra (IT);FEDUZI R, JRC Ispra (IT);INZAGHI D, JRC Ispra (IT);MANARA A, JRC Ispra (IT);ZOCCHI M, University of Brescia, Department of Mechanical Engineering, Brescia (IT)
Bibliographic Reference: Paper presented: International Conference on Materials and Mechanisms of Superconductivity and High-Temperature Superconductors, Kanazawa (JP), July 22-26, 1991
Availability: Available from (1) as Paper EN 36240 ORA
Record Number: 199110811 / Last updated on: 1994-12-02
Original language: en
Available languages: en