Modulated Structure of the High-Tc Superconductor Bi-Pb-Ca-Sr-Cu-O Studied by High-Resolution Electron Microscopy and Electron Diffraction

Abstract
A new type of atomic displacive modulation in the incommensurate superconducting oxide Bi-Pb-Ca-Sr-Cu-O (2223 phase) has been studied by high-resolution electron microscopy and electron diffraction. The structure is orthorhombic with cell dimensions a=0.54, b=4.2 (∼8a) and c=3.71 nm. The structural modulation has been analyzed by assuming a commensurate cell with the dimension b=8a. The intensity distribution of superstructure reflections can be well explained by taking atomic displacive longitudinal and transverse waves into account.