Structural description of high-Tc cuprate superconductors

Ognjen Milat; Gustaaf Van Tendeloo; Severin Amelinckx

doi:10.1117/12.250232

5 July 1996 Structural description of high-T_c cuprate superconductors

Ognjen Milat, Gustaaf Van Tendeloo, Severin Amelinckx

Proceedings Volume 2697, Oxide Superconductor Physics and Nano-Engineering II; (1996) https://doi.org/10.1117/12.250232
Event: Photonics West '96, 1996, San Jose, CA, United States

Abstract

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 were widely detected. The superstructures are due to cation and/or oxygen atom ordering mainly in the MO_1-x 'chain' layer, while the remaining part of the structure is hardly affected. The superlattice based on the 2 (root) 2a_p X (root) 2a_p X c_p orthorhombic cell is found in the Co-1212 and Ga-12n2 compounds; a commensurate superstructure based on the 4a_p X 2a_p X c_p orthorhombic cell in the Al-1222 compound, and an incommensurate modulated structure on the monoclinic cell 3.43a_p X a_p X 1.15c_p in the S-1212 compound. A rock-salt layer ordering on the two-dim 2a_p X 2a_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 CuO₂ planes on a 2 (root) 2a_p X 2 (root) 2a_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 CuO₂-'block'-layers, which tends to preserve tetragonal symmetry regardless of the number of constituting perovskite, rock-salt, or fluoruite type layers.

Citation Download Citation

Ognjen Milat, Gustaaf Van Tendeloo, and Severin Amelinckx "Structural description of high-T_c cuprate superconductors", Proc. SPIE 2697, Oxide Superconductor Physics and Nano-Engineering II, (5 July 1996); https://doi.org/10.1117/12.250232

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