Study on the formation of the liquid phase during heating process of Bi-2223/Ag superconducting tapes at various oxygen partial pressure by using in situ resistance measurement

The resistance of T-phase tape and O-phase tape was in situ measured during heating at various oxygen partial pressures. The resistance increased at a characteristic temperature, which was related to the formation of the liquid phase. The formation temperature of the liquid phase increased with increasing oxygen partial pressure. And the formation temperature of the liquid phase of T-phase tape was about 6 deg. C higher than that of O-phase tape. Two kinds of green mono-filament Bi-2223/Ag superconducting tapes (T-phase tape and O-phase tape) were investigated, the initial superconducting phase of which was tetragonal Bi-2212 phase and orthorhombic (Bi,Pb)-2212 phase, respectively. The resistance of these tapes was in situ measured during heating at various oxygen partial pressures. It was found that the resistance increased at a characteristic temperature at every oxygen partial pressure. This resistance behavior was related to the formation of the liquid phase. The formation temperature of the liquid phase increased with increasing oxygen partial pressure. And the formation temperature of the liquid phase of T-phase tape was about 6 deg. C higher than that of O-phase tape. The above results demonstrated that the in situ resistance measurement is a sensitive method for studying the formation of the liquid phase in superconducting materials.