The replacement of [HgO{sub 2}]{sup 2-} by the tetrahedral sulfate anion [SO{sub 4}]{sup 2-} in the Hg-1201 superconductor
Journal Article
·
· Journal of Solid State Chemistry
- Laboratorie de Cristallographie, Grenoble (France); and others
The possibility of existence of a Hg{sub 1-x}S{sub x}Ba{sub 2}CuO{sub 4+2x+{delta}} solid solution [(Hg, S)-1201] was studied at 18 kbar and 920{degrees}C. Monophasic samples were obtained in the range 0.00 < x < 0.15, where the unit cell parameters were found to vary from a=3.8685 (1) {Angstrom}, c=9.4667(2) {Angstrom} for x = 0.00 to a=3.9010(1) {Angstrom} and c = 9.3048(6) {Angstrom} for a nominal composition x = 0.30. The as-prepared phases with 0.00 < x < 0.05 were found to be nonsuperconducting due to overdoping, while superconductivity appeared at x = 0.10 (T{sub c,onset}=40K). T{sub c} increases with the amount of sulfate substitution due to the decrease of the average copper valence. For the annealed samples, the variation is opposite to that found for the as-prepared samples, T{sub c,onset} being higher for the sulfur-free phase. Rietveld refinements of neutron powder diffraction data has determined {approximately} 18% of the HgO{sub 2}{sup 2-} dumbbells to be substituted by SO{sub 4}{sup 2-} groups. In this structure the SO{sub 4}{sup 2-} anion adopts an average S-O bond length that is slightly higher than those in BaSO{sub 4}.
- OSTI ID:
- 223708
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 1 Vol. 121; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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