Crystal structure-Tc correlations in LaBa1.5Ca0.5Cu3Oδ

J. M.S. Skakle* (Corresponding Author), A. R. West

*Corresponding author for this work

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The structure of superconducting LaBa1.5Ca0.5Cu3Oδ (LaBCCO) was refined by the Rietveld method using powder neutron diffraction (ND) data. Data sets were collected at both room temperature and high temperature (HT). For the room temperature data, samples were heated isothermally over a range of temperatures to give a range of oxygen contents and then either cooled slowly or quenched. HT data were recorded in isothermal steps over the range 300-900 °C in vacuum. The structure is similar to that of YBCO but with the A-cation distribution [La0.5Ca0.5][La0.5Ba1.5]Cu3 Oδ; variable oxygen content is accommodated by changes in occupancy of the basal plane sites and the samples remain tetragonal under all conditions. Layers of Cu(2)O5 pyramids are connected via apical oxygens O(3) to Cu(1) atoms. The Cu(2)-O bond distances vary smoothly with δ, have similar values for all three data sets and are insensitive to critical temperature (Tc) variations seen between quenched and slowly cooled samples for a given δ. The Cu(1)-O(3) bond distances show a range of dependencies on δ and appear to correlate with Tc, even though the superconductivity cannot reside with Cu(1) due to the absence, in this tetragonal structure, of infinite Cu(1)-O chains which could have provided a long-range conduction pathway. These results, in which the composition dependence of the Cu(1)-O(3) bond length appears to reflects that of Tc, are in complete contrast to data on YBCO which show that Cu(2)-O(3) is the key structural parameter that mirrors Tc.

Original languageEnglish
Pages (from-to)12-28
Number of pages17
JournalPhysica C: Superconductivity and its Applications
Volume321
Issue number1-2
DOIs
Publication statusPublished - 1 Aug 1999

Keywords

  • neutron diffraction
  • Rietveld refinement
  • Cu-O bond lengths
  • critical temperature

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