Effects of oxygen doping and structural distortion on the superconductivity of single crystals

Abstract

Effects of oxygen doping and structural distortion on the superconductivity of (Bi2212) were studied by ac susceptibility and x-ray diffraction measurements for a group of high-quality single crystals. The crystals were annealed at 600 and under different oxygen pressures ranging from to 6080 Torr. It was found that the c-axis length showed a plateau at - Torr and decreased with increasing oxygen pressure above Torr, which strongly suggested that two stages of oxygen diffusion may be involved. The full width at half maximum (FWHM) of the 00 main reflection, which reflects structural distortion in the c direction, showed a peak around the optimized oxygen doping. This implies that the structural modification may be another factor that affects apart from oxygen content. On the other hand, the period of incommensurate modulation along the b direction, s, was found to have nothing to do with the oxygen content or superconductivity. Relationships between superconductivity, oxygen content and microstructure of the Bi2212 single crystal are discussed.