Please use this identifier to cite or link to this item: http://lib.jncasr.ac.in:8080/jspui/handle/10572/1256
Title: 123, 247, and 124 cuprate superconductors: Investigations of thermodynamic stabilities, defect structures, and intergrowths
Authors: Rao, C N R
Subbanna, G N
Nagarajan, R
Ganguli, A K
Ganapathi, L
Vijayaraghavan, R
Bhat, S V
Raju, A R
Keywords: cuprate superconductors
thermodynamic stabilities
X-ray diffraction
electron microscopy
Issue Date: Sep-1990
Publisher: Academic Press Inc JNL-Comp Subscriptions
Citation: Journal of Solid State Chemistry 88(1), 163-176 (1990)
Abstract: Careful investigations employing nonresonant microwave or rf absorption, Cu2+ EPR spectra, X-ray diffraction, and electron microscopy show that orthorhombic YBa2Cu3O7−δ is thermodynamically stable and monophasic when δ is 0.0–0.2 (Tc = 90 K), 0.25 (Tc = 80 K), and 0.5 (Tc = 45 K). The last two compositions are associated with ordered oxygen-vacancy structures; in the δ = 0.0–0.2 regime, 3b = c. Compositions in the range δ = 0.3–0.4 (Tc = 60 K) do not appear to be thermodynamically stable and decompose on annealing, suggesting thereby that the so-called 60 K superconducting phase in the YBa2Cu3O7−δ system may not be genuine. 123 cuprates prepared with excess CuO often show fringes of 124 in lattice images. Both 124 and 247 cuprates prepared by the ceramic method in a flowing oxygen atmosphere frequently show intergrowths of each other or with 123. Such epitaxial relationships between 123, 124, and 247 cuprates could be of significance with respect to their superconducting properties. Both 124 and 247 cuprates undergo thermal decomposition to give 123 and CuO.
Description: Restricted Access
URI: http://hdl.handle.net/10572/1256
Other Identifiers: 0022-4596
Appears in Collections:Research Papers (Prof. C.N.R. Rao)

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