The replacement of [HgO2]2- by the tetrahedral sulfate anion [SO4]2- in the Hg-1201 superconductor

S. M. Loureiro, P. G. Radaelli, E. V. Antipov, J. J. Capponi, B. Souletie, M. Brunner, M. Marezio

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8 Citations (Scopus)

Abstract

The possibility of existence of a Hg1-xSxBa2CuO4+2x+δ solid solution [(Hg, S)-1201] was studied at 18 kbar and 920°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) Å, c = 9.4667(2) Å for x = 0.00 to a = 3.9010(1) Å and c = 9.3048(6) Å for x = 0.15. Samples with x ≥ 0.20 were polyphasic and the unit cell parameters of the [(Hg, S)-1201] phases were found to vary up to a = 3.9072(1) Å, c = 9.2654(5) Å 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 (Tc,onset = 40 K). Tc 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, Tc,onset being higher for the sulfur-free phase. Rietveld refinements of neutron powder diffraction data has determined ≈18% of the HgO2-2 dumbbells to be substituted by SO2-4 groups. In this structure the SO2-4 anion adopts an average S-O bond length that is slightly higher than those in BaSO4.

Original languageEnglish
Pages (from-to)66-73
Number of pages8
JournalJournal of Solid State Chemistry
Volume121
Issue number1
DOIs
Publication statusPublished - 5 Jan 1996
Externally publishedYes

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