An electron diffraction study of superconducting oxides Ba1−xPbxBiO3 and Ba1−yPbyBiO3

Abstract

Before the discovery of superconductivity in La-Ba-Cu-O by Bednorz and Müller, it has been known that BaPb1−xBixO3 (BPB) exhibits superconductivity below about 13 K. In particular, because Ba1−yKyBiO3 (BKB) was found to be a superconductor with Tc of about 30 K, the Ba-oxides become more important in order to understand the mechanism of superconductivity of the oxide superconductors. Characteristic features for the Ba-Oxides are that their crystal structure is basically the cubic perovskite structure and there is not a Cu-O layer which is responsible for the superconductivity in the oxide superconductors having the Cu-O layer, such as Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O. That is, the O(2p)-[Pb(6s), Bi(6s)] hybridized orbitals would play an important role in the case of the Ba-oxides. In the present work, in order to understand features of the crystal structure of the Ba-oxides, including a structural disorder, the details of the structure have been examined by means of electron diffraction.