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.