Relationships between the structural properties and the superconductivity in Y0:4Pr0:6Ba2-xSrxCu3O7-δ (x = 0;1:0)

The Y_0:4Pr_0:6Ba_2-xSr_xCu₃O_7-δ (x = 0;1:0) samples were prepared and the structural properties were studied by X-ray Rietveld analysis. It has been found that the average Pr-O bond length increases from 2.435Å at x = 0 to 2.457Å at x = 1:0, the Cu(2)-O-Cu(2) angles within the CuO₂ planes become larger, and there is no significant mutual substitution between Pr and Sr ions. The BVS calculation suggests that Sr doping brings about the increase of the hole concentration on CuO₂ planes and the weakening of Pr-O covalent mixing. Our work supports that Pr-O covalent mixing effect is responsible for the superconductivity suppression by Pr.