Crystal Structures of YBa2Cu3Ox and LnBa2Cu3Ox (Ln = Ho and Dy)

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Abstract
Structure determinations of YBa2Cu3O x and LnBa2Cu3O x (Ln = Ho and Dy) are carried out by single crystal X-ray diffraction. The x values obtained in the present analyses are about 6.0, 6.0 and 6.25 for Y, Ho and Dy compounds, respectively and they have tetragonal structure with space group P4/m m m. The structures are perovskite-related ones with the c axis triplicated due to the ordering of Ba and Y or Ln. All oxygen atom sites around Y or Ln atoms in the c plane are vacant. Almost all oxygen atom sites in the layers which contain the Cu(1) sites (4/m m m) are also vacant. The present YBa2Cu3O6 crystal is found to be a semiconductor, which indicates the importance of the oxygen number for the occurrence of superconductivity in Y-Ba-Cu-O and Ln-Ba-Cu-O systems.