Investigation on the phase transformation of Bi-2223/Ag superconducting tapes during heating

• In situ resistance measurement was carried out on Bi-2223/Ag superconducting tapes.
• The oxygen partial pressure of the outlet gas in the heating process was monitored continuously.
• The samples quenched in the heating process were studied by XRD and Tc measurements.
• The heating process contains three procedures: oxygen diffusion, Pb-rich phase evolution and liquid phase formation.

The phase transformation of Bi-2223/Ag superconducting tapes during heating was investigated. The resistance of the ceramic core as a function of the heating temperature was measured in situ. The pO2 of the outlet gas in the heating process was also monitored continuously. By comparing the heating process with the X-ray diffraction and Tc measurements taken from samples quenched at different temperatures, we have identified that the heating process could be divided into the following regions: (1) the oxygen diffusion (OD) region, which is mainly influenced by OD; (2) the Pb-rich phase evolution (PbE) region, in which the formation and decomposition of the Pb-rich phases occur; (3) the liquid phase formation (LF) region, in which resistance increased rapidly with increasing temperature.