| Original Articles |
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Effect of Oxygen-Diffusion Possibly Involved in Perovskite Unit on Superconductivity of Various Oxygen-Doped Bi2Sr2CaCu208+y Single Crystals |
| ZHAO Xiao-ru;SUN Xue-feng;WU Wen-bin;JIA Yun-bo;ZHOU Gui-en;LI Xiao-guang;ZHANG Yu-heng1 |
| Structure Research Laboratory, University of Science and Technology of China, Hefei 230026
1CCAST (World Laboratory), P. O. Box 8730, Beijing 100080, and Structure Research Laboratory, University of Science and Technology of China, Hefei 230026
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| Cite this article: |
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ZHAO Xiao-ru, SUN Xue-feng, WU Wen-bin et al 1997 Chin. Phys. Lett. 14 613-616 |
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Abstract For a highly oriented Bi2Sr2CaCu208+y single crystal with a lower as-grown Tc of 72K, on air-annealing at 250°C for 2h, its Tc remained unchanged, while increased to 83 K after annealing for 25 h. For another crystal with a higher as-grown Tc of 86.7K and annealed under the same condition, its Tc was unchanged except for a slight improvement of ΔTc and was independent of the annealing time. X-ray diffraction showed that there were no changes of c-axis lattice parameter for the annealed crystals. If the above two crystals, after annealing at 250°C for 25 h, were further annealed at 600°C for 20 h, then Tc was increased to the same value of almost 88K and the c-axis lattice parameter showed a dramatic contraction. We suggested that the improvement of superconductivity of the sample annealed at much lower annealing temperature (250°C ) are associated with the oxygen diffusion involved in the pervoskite unit and this diffusion from the perovskite unit occurs earlier than that from Bi-O layers.
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| Keywords:
74.60.-w
74.70.-b
66.30.-h
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Published: 01 August 1997
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