High-Resolution Electron Microscopy of Modulated Structure in the New High-T_c 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 Bi 4 Sr 3 Ca 3 Cu 6 O x and Bi 4 Sr 3 Ca 2 Cu 4 O 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 Bi 2 O 2 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.