Neutron structural investigations of Y{sub 1-x}Ca{sub x}Ba{sub 2}Cu{sub 3-y}Co{sub y}O{sub 7{+-}{delta}}
Journal Article
·
· Journal of Superconductivity
- Bhabha Atomic Research Centre, Bombay (India); and others
The results of a systematic powder neutron study on Y{sub 1-x}Ca{sub x}Ba{sub 2}Cu{sub 3-y}Co{sub y}O{sub 7{+-}{delta}} for A (x=y=0), B(x=0; y=0.2), C (x=0; y=0.4), D (x=y=0.2), and E (x=y=0.4) are investigated with a view to understanding the relation between the structural parameters and superconductivity. Rietveld refinements of the structures show that: (a) Co substitutes at the chain Cu(1) sites only, except for sample, E, where the presence of a minor amount of Co at the planar Cu(2) site cannot be rules out; (b) Co substitution reduce the c-parameter, which is reduced even further upon substitution of Ca at the Y-sites; (c) the occupancy factors of the chain O(1) site indicate an average coordination of 4.8 and 5.1 for Co for samples B and C, but only 4 for D and E; (d) Cu/Co(1) atoms for B and C display large thermal parameters, suggesting a displacement from their ideal centrosymmetric locations; (e) the apical Cu(1)-O(4) bond lengthens upon substitution of Co in samples B and C but undergoes shortening upon substitution of Ca in the case of samples D and E. The apical Cu(2)-O(4) bond, on the other hand, shows just the opposite trend; (f) samples D and E show a reduction in the separation of CuO{sub 2} layers and their oxygen content; and (e) the bond valence of the Cu(2) ion shows the lowest value of 2.127 for the nonsuperconducting sample C.
- OSTI ID:
- 102683
- Journal Information:
- Journal of Superconductivity, Journal Name: Journal of Superconductivity Journal Issue: 2 Vol. 8; ISSN JOUSEH; ISSN 0896-1107
- Country of Publication:
- United States
- Language:
- English
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