(Pb,Cu) (Sr,Nd)2(Ho,Ce)2Cu2Oz (z≈8.64) was made superconducting by heating at 500°C in O2 at a pressure of 90 atm. This oxide had a transition temperature (Tc) 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.
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