Anomalous high temperature electrical behaviors in Bi₂Sr₂CaCu₂O_y oxides

The high temperature resistivity (27 - 900 °C) and the x-ray diffraction (27 - 500 °C) have been measured to investigate the anomalous transport behaviors in 90 K Bi₂Sr₂CaCu₂O_y (BSCCO) oxides. A very sharp peak in the high temperature resistivity measurement was observed to occur at a specific temperature Tp as the BSCCO samples were exposed to various gas environments. These specific temperatures are at 275 °C, 389 °C and 450 °C respectively for BSCCO samples in the oxygen (1 atm), vacuum (1 mtorr) and the flowing helium (1 atm) environments. No significant decomposition was detected by the powder x-ray diffraction at temperatures near Tp ± 100 °C. The x-ray diffraction data suggest that the change in the lattice parameters possibly causes the sharp peak of the high temperature resistivity data; which therefore affects the superconducting transition temperature of BSCCO samples.