Identification of Pb-doped Bi-Sr-Ca-Cu-O superconducting phases by convergent beam electron diffraction

Abstract

Pb-doped Bi2Sr2Ca2Cu3O10 (2223) and Bi2 Sr2 Ca3 Cu4 O12 (2234) superconducting phases have been identified by convergent beam electron diffraction. The c parameters of the 2223 and 2234 phases are 37.6 and 44 Å, respectively. The two phases have the same symmetry; their common point group is mmm. Both phases are modulated, but the modulations are different from and considerably weaker than that in the unleaded Bi2 Sr2 CaCu2 O8 . This work confirms for the first time the existence of the 2234 phase.