Crystal Structure of the (K0.87Bi0.13)BiO3Superconductor

The structure of a superconducting oxide (K0.87Bi0.13)BiO3(Tc10.2 K) prepared under high pressure was analyzed by time-offlight neutron powder diffraction. Rietveld refinement showed this compound to be a cubic perovskiteABO3with space groupPm m(No. 221) and lattice parametera=4.23377(3) ?. Refinement of occupation factors revealed the absence of oxygen vacancies and the substitution of Bi3+ions for 13% of K+ions at theAsite, presenting evidence for electron doping in this superconductor. Extraordinarily large atomic displacement parameters for theAand O sites are believed to reflect pronounced positional disorder mainly arising from the large difference in size between the K+and Bi3+ions.