High-Resolution Electron Microscopy of Modulated Structure in the New High-Tc Superconductors of the Bi-Sr-Ca-Cu-O System

Abstract

Both high-T _c (105 K) and low-T _c (75 K) superconducting oxides recently reported by Maeda et al. (Jpn. J. Appl. Phys.: in press) are examined by transmission electron microscopy with an EDX analysis. The chemical compositions are estimated to be Bi₄Sr₃Ca₃Cu₆O _x and Bi₄Sr₃Ca₂Cu₄O _y for high- and low-T _c samples. The diffraction patterns and high-resolution structure images show that the compounds have layered structures with alternate Bi₂O₂ layers and perovskite ones in a c-direction. A high-resolution image projected along the a-axis clearly shows the presence of the modulated structure with lattice curving.