RELATIONSHIPS BETWEEN THE STRUCTURAL-PROPERTIES AND THE SUPERCONDUCTIVITY IN Y0.4PR0.6BA2-XSRXCU3O7-DELTA (X=0, 1.0)

The Y0.4Pr0.6Ba2-xSrxCu3O7-delta (x = 0, 1.0) samples were prepared an d the structural properties were studied by X-ray Rietveld analysis. I t has been found that the average Pr-O bond length increases from 2.43 5 Angstrom at x = 0 to 2.457 Angstrom at x = 1.0, the Cu(2)-O-Cu(2) an gles within the CuO2 planes became larger, and there is no significant mutual substitution between Pr and Sr ions. The BVS calculation sugge sts that Sr doping brings about the increase of the hole concentration on CuO2 planes and the weakening of Pr-O covalent mixing. Our work su pports that Pr-O covalent mixing effect is responsible for the superco nductivity suppression by Pr.