STRUCTURAL-CHANGES ACCOMPANYING OXYGEN INCORPORATION IN (PB0.65CU0.35)SR2(Y0.7CA0.3)CU2O7+DELTA

The structure parameters of superconducting (Pb0.65Cu0.35)Sr2(Y0.7Ca0.3)Cu2O7.0 and nonsuperconducting (Pb0.65Cu0.35)Sr2(Y0.7Ca0.3)Cu2O7.1 were refined by the Rietveld analysis of their TOF neutron powder diffraction data. These oxides are tetragonal with the P4/mmm space group are closely related in structure to TlBa2CaCu2O7 and YBa2Cu3O7. The excess oxygen contained in the nonsuperconducting compound interstitially occupies a 2f site on a (Pb, Cu)O layer. Slight decreases in Cu(2)-O(1) and Cu(2)-O(2) bond lengths induced by removing excess oxygen reflect an increase in hole concentration on a CuO2 plane. However, shrinkage of these Cu(2)-O bonds accompanying oxygen removal is so subtle that the bond valence sum of a Cu ion on the CuO2 plane in the superconducting compound (2.28) is only slightly larger than that in the nonsuperconducting one (2.26).