Abstract
The evolution of the phase formation in (Bi,Pb)-Sr-Ca-Cu-O superconducting materials prepared by the co-precipitation method has been investigated by X-ray diffraction analysis. Formation of the desired 2223 phase was found to proceed through a complicated reaction route of forming the single, double and triple Cu-O layered superconducting structures in sequence with increasing temperature. The phase with a more Cu-O layered structure was found to grow at the expense of the less Cu-O layered phase. Several intermediate phases of Bi-Sr/Ca-O compounds were found to be closely related to the formation of the superconducting phase with single and double Cu-O layered structures. The investigation of the kinetics of forming the 2223 phase revealed that two mechanisms dominated the reaction rate in the early and late stages of growing the 2223 phase. c 1998 Elsevier Science B.V.