Torardi, C. C. ; Parise, J. B. ; Subramanian, M. A. ; Gopalakrishnan, J. ; Sleight, A. W. (1989) Oxygen nonstoichiometry in copper-oxide based superconductors and related systems: structure of nonsuperconducting Bi2Sr3-xYxCu2O8+y (x≈0.6-1.0) Physica C: Superconductivity, 157 (1). pp. 115-123. ISSN 0921-4534
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Official URL: http://linkinghub.elsevier.com/retrieve/pii/092145...
Related URL: http://dx.doi.org/10.1016/0921-4534(89)90476-0
Abstract
Structural refinements of the new compounds Bi2Sr3-xYxCu2O8+y in the range of x that gives insulating rather than superconducting behaviour (x≈0.6 and 1.0) have been obtained from single crystal X-ray and neutron powder diffraction data. Results indicate oxygen nonstoichiometry and suggest condensation into pairs or chains of the Bi---O atoms along the a axis in the Bi---O double layers. Chain-like formation can be found between the copper-oxygen sheets of all the orthorhombic superconductors including La2CuO4. XANES studies show that the oxidation state of copper (Cu2+ is not affected by yttrium substitution for strontium. The mechanism of charge compensation appears to involve the insertion of oxygen, over the ideal O8 composition, in (rather than between) the Bi---O sheets. These materials are orthorhombic and the lattice parameters for the subcell of the x≈0.6 material are a=5.467(3), b=5.4407(6), c=30.434(5) Å, space group Amaa, Z=4. The x≈1.0 phase has a=5.467(2) b=5.426(1), and c=30.183(8) Å. The structure is essentially the same as that of superconducting Bi2Sr3-xCaxCu2O8+y. Electron diffraction patterns for the yttrium-containing phases show an incommensurate superlattice along the a axis as seen in the calcium analog. This is due to atomic displacements that are modulated along a with amplitudes in the c direction.
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ID Code: | 12250 |
Deposited On: | 10 Nov 2010 04:59 |
Last Modified: | 03 Jun 2011 05:02 |
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