Bulk superconductivity near 9 K has been observed in BaPb0.5Bi0.25Tl0.25O3-δ. Superconductivity is observed in samples that have been prepared by a three-step process, using sequential anneals in Ar, O2 and 5% O2-95% Ar (at 775°C, 475°C and 650°C, respectively). Samples annealed at 600°C after the third step in pure Ar are not superconducting, but remain superconducting after pure O2 annealing. Structural studies have been carried out by Rietveld refinement of neutron powder data for samples in both the superconducting regions and the pure Ar annealed nonsuperconducting region. All three systems have essentially identical tetragonal structures at 305 K, with space group I4/mcm. The (0, 0, 1 4) oxygen site is displaced to the four-fold (x, 0, 1 4) s ite and probably fully occupied; the (x, x+ 1 2, 0) site appears approximately 6% deficient for the Ar annealed sample and 4% deficient for the other two samples. The title compound represents the first thallium substituted non-copper oxide superconductor and hence some of its characteristics are briefly compared with that of the isomorphous BaPb0.75Bi0.25O3 (Tc=13 K) and BaPb0.75Sb0.25O3 (Tc=3.5 K) superconductors.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering