Structural description of high-{Tc} cuprate superconductors
- Univ. of Zagreb (Croatia). Inst. of Physics
- Univ. of Antwerp (Belgium)
A number of high-{Tc} superconducting cuprate phases related with YBCO were studied by means of high resolution electron microscopy and electron diffraction. The lower symmetry superstructures in which Cu atom in the chain layers is substituted by M (= Ga, Co, Al, Hg, C, S,...) were widely detected. The superstructures are due to cation and/or oxygen atom ordering mainly in the MO{sub 1{minus}x} chain layer, while the remaining part of the structure is hardly affected. The superlattice based on the 2 {radical}2a{sub p} x {radical} 2a{sub p} x c{sub p} orthorhombic cell is found in the Co-1212 and Ga-12n2 compounds; a commensurate modulated structure on the monoclinic cell 3.43a{sub p} x a{sub p} x 1.15c{sub p} ({beta} = 120{degree}) in the S-1212 compound. A rock-salt layer ordering on the two-dim 2a{sub p} x 2a{sub p} superlattice was observed in the Ga-1222 compound; it appears as a consequence of partial replacement of Ba for Sr in the (Sr/Ba)O-GaO-(Sr/Ba)O lamella. A two-dim modulation in the CuO{sub 2} planes on a 2 {radical}2a{sub p} x 2{radical}2a{sub p} superlattice was detected in the vacuum heated YBCO (Cu-1212), Al-1222, and Bi-2212 compounds. All these studies support the concept of cuprate superconductor structure as an alternating stack of MO-chain layers, whose structure determines the overall symmetry, and the CuO{sub 2}-block-layers, which tends to preserve tetragonal symmetry regardless of the number of constituting perovskite, rock-salt, or fluorite type layers.
- OSTI ID:
- 548455
- Report Number(s):
- CONF-960163--; ISBN 0-8194-2071-9
- Country of Publication:
- United States
- Language:
- English
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