Hole Donors in the High-Tc Phase of a Bi-Pb-Sr-Ca-Cu Oxide Superconductor

The locations of Sr atoms in a crystal of the Bi-Pb-Sr-Ca-Cu oxide superconductor consisting of the high-T c phase were studied by high-resolution analytical electron microscopy (HRAEM) with a spatial resolution of 17 Å using a probe 5 to 10 Å in diameter. The HRAEM showed that not only Pb atoms, but also Sr atoms were located in the Bi-O layers, indicating that these atoms might be hole donors in the Bi-Pb-Sr-Ca-Cu-O superconductor.