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Science 2 February 1990:
Vol. 247. no. 4942, pp. 553 - 556
DOI: 10.1126/science.247.4942.553
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Articles

Direct Observation and Analysis of CuO2 Shear Defects in La2-xSrxCuO4

Pratibha L. Gai 1 and Eugene M. McCarron III 1

1 Central Research and Development Department, E. I. DuPont de Nemours Inc., Experimental Station, Wilmington DE 19880

Direct observations of CuO2 sheet defect structures in superconducting La2-xSrxCuO4, with x in the range 0.05 le x le 0.15, are reported. Electron microscopy shows that extended line defects are generated in {010} planes, along <206> crystallographic directions, by a pure shear mechanism along the edge of the octahedral copper-oxygen units. The line defects are partial screw dislocations, with characteristic displacement vectors of the type <(a/2), 0, (c/6)>, bounding the stacking faults. The existence of this type of defect demonstrates that there is an oxygen deficiency within the CuO2 layers. However, unlike the open ReO3 type-related structures, the packing density of the K2NiF4 structure necessarily requires that anion defects be accompanied by the loss of cations of the A type (lanthanum, strontium). Under identical synthesis conditions, no defects are observed in the parent compound La2CuO4.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Solid-State Defect Mechanism in Vanadyl Pyrophosphate Catalysts: Implications for Selective Oxidation.
P. L. Gai and K. Kourtakis (1995)
Science 267, 661-663
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