Ｂｉ系超伝導体の高温電気抵抗

Abstract

The high temperature behaviors of Bi-Sr-Ca-Cu-O and Bi(Pb)-Sr-Ca-Cu-O superconductors were investigated by electrical resistivity measurement and X-ray diffraction in relation to superconducting properties. (1) For BiSrCaCu2 Oy: Two peaks in the temperature dependence of the electrical resistivity were detected at 300 and 650°C on heating process, but no peak was detected on cooling process. (2) For Bi0.7 Pb0.3 SrCaCu1.8 Oy: Two peaks were also detected at 300 and 650°C for the samples with Low-Tc phase, but they decreased with increasing content of High-Tc phase in the samples and finally disappeared for the samples with almost High-Tc single phase. (3) For Bi2 Sr2 CaCu2 Oy: The peaks detected in the electrical resistivity on heating process became more apparent than those of the other samples described above. From these results, it may be concluded that the peaks in the electrical resistivity detected at 300 and 650°C are due to the Low-Tc phase, High temperature X-ray diffraction showed that no change was observed at 300°C, but Low-Tc phase seemed to decompose at 650°C. Further detailed research is in progress.