Oxygen-Diffusion and Structural Modification in Air-Annealed Superconducting Bi2Sr2CaCu2Oy Single Crystals
ZHAO Xiao-ru1,3, WU Wen-bin1, SUN Xue-feng1, WANG Liang-bin1, ZHOU Gui-en1, LI Xiao-Guang1, ZHANG Yu-heng1,2, Koichi Kitazawa3
1Structure Research Laboratory, University of Science and Technology of China, Hefei 230026
2CCAST (World Laboratory), P.O. Box 8730, Beijing 100080
3Department of Applied Chemistry, Department of Superconductivity, University of Tokyo, 7-3-1 Hongo, Bunkyo 113, Japan
Oxygen-Diffusion and Structural Modification in Air-Annealed Superconducting Bi2Sr2CaCu2Oy Single Crystals
1Structure Research Laboratory, University of Science and Technology of China, Hefei 230026
2CCAST (World Laboratory), P.O. Box 8730, Beijing 100080
3Department of Applied Chemistry, Department of Superconductivity, University of Tokyo, 7-3-1 Hongo, Bunkyo 113, Japan
Abstract： Bi2Sr2CaCu2Oy single crystals were air-annealed at 300, 400, 600 and 750°C for 20h in consequence. Measurements of ac susceptibility and x-ray diffraction showed that at annealing temperature below 400°C, the change of Tc was dominated by oxygen-diffusion involved in pervoskite unit and was strongly sample-dependent. This diffusion from pervoskite unit occurred earlier than that from Bi-O layers. At annealing temperature over 400°C, with the intercalation of excess oxygen into Bi-O layers, the hole concentration in the crystal was redistributed so that Bi-O reservoir fully determined superconductivity. From the changes of non-uniform strain in annealing process, it was found that structural modification was also closely correlated to superconductivity.
1997, Vol. 14 
