Structural Characteristics of 2212-Phase Single Crystal in the Bi-Sr-Ca-Cu-O Superconductor

A single crystal of Bi-Sr-Ca-Cu-O 2212 superconducting phase has been studied by combining the Laue method with the method of X-ray diffractometry. It is suggested that the single-crystal structure of a superconductor is a modulated structure of a three-dimensional period coexisting with a two-dimensional lattice. In the structure, the Bi-concentrated bands, which form a three-dimensional modulated structure that corresponds to the results observed in high-resolution electron microscopy, do not entirely enter the parent structure lattice, but divide the parent structure into oxygen-deficient pervoskitelike layers. The pervoskitelike layer has a quasi-two-dimensional structure. The element modulation of Sr and Ca appears in the two-dimensional lattice, which is caused by the effect of Bi-concentrated bands. Meanwhile, the superlattice is formed on the ab plane. The three-dimensional structure of periodic modulation is formed by the pervoskitelike layer and Bi-concentrated band as a unit.