The structural effects of the substitution of Pr for Y in Y2Ba4Cu7O15-d are studied by Rietveld analysis of neutron powder diffraction data. Comparisons are made with Pr substituted Y-123 and Y-124. A series of samples with nominal composition (Y1-xPrx)2Ba4Cu7O 15-d, where x was varied between x = 0.0 and 1.0, was prepared by a polymerised complex method and sintered at 1 atm pressure in oxygen. The limit of solubility was found to be x ≈ 0.6. Susceptibility measurements show that Tc,onset decreases from 94.8 K to 39 K at x = 0.6. The cell parameters and volume increase with Pr substitution. The volume expansion is observed to be equal to the sum of the respective volumes expansions for Pr doped Y-123 and Y-124 at the same Pr content. The calculated bond distances show that the substitution causes an expansion of the interplane distance around the Y(Pr) site, which is largely compensated by the compression of the CuO chain regions. In general, the observed atomic displacements in the three phases with Pr substitution, may be explained as an effect of the strain exerted by the expansion of the interplane distance. An analysis of the bond valence sums for the metal ions was carried out to show how the internal stresses change with doping in these systems.
ASJC Scopus subject areas