STRUCTURAL-PROPERTIES OF (PB,CU)(SR,ND)2(HO,CE)2CU2O9-DELTA

(Pb,Cu)(Sr,Nd)2(Ho,Ce)2Cu2Oz (z almost-equal-to 8.64) was made superconducting by heating at 500-degrees-C in O2 at a pressure of 90 atm. This oxide had a transition temperature (T(c)) around 10 K. Its structure parameters were refined by the Rietveld method using neutron powder diffraction data. This compound belongs to space group 14/mmm and has a tetragonal unit cell with lattice constants, a = 0.382496(8) nm and c = 2.89862(7) nm. Atoms in fluorite-type layers and CuO2 planes are firmly bound at their ideal positions, whereas a (Pb,Cu)O monolayer is highly disordered and defective. In addition, an apical oxygen site in a [CuO5] pyramid is about 13% deficient. Such lattice instability in this oxide is discussed in connection with structural defects in other copper oxides.