Synthetic Conditions and Structural Properties of the High-Tc Phase in the Superconducting Bi-Sr-Ca-Cu-(Pb)-O System
Synthetic conditions, structural and thermal properties of the high-Tc phase (Tc > 100 K) in the Bi-Sr-Ca-Cu-O system have been investigated. Three methods have been found to be effective in increasing the volume fraction of the high-Tc phase in the Bi-Sr-Ca-Cu-0 system: (1)starting from a nominal composition with more Ca and Cu than Bi2Sr2Ca2Cu3O (2) the addition of Pb to Bi-Sr-Ca-Cu-0 system (3) annealing at 870°C under higher oxygen partial pressures than 0.2 atm. Sample with the nominal composition of Bi2Sr2Ca6Cu8Ox fired at 87O°C for 120 hours was found that it consisted of mainly the high-Tc phase. Unit cell dimensions of the high-Tc phase determined by X-ray powder diffraction and transmission electron diffraction measurement are a = 5.40 Å, b = 27.0 Å and c = 36.8 Ä, indicating a pseudotetragonal symmetry. Transmission electron microscopy showed that there were stacking faults in the high-Tc phase. The high-Tc phase and the low-Tc phase (T ~ 80 K) decompose into Bi2Sr2CuOx by annealing under oxygen partial pressure of 0.02 and 0.1 atm at 87O°C. Under higher oxygen partial pressures than 0.2 atm at 870°C, the high-Tc phase was remarkably formed from the possible disproportionation reaction of the low-Tc phase.
KeywordsOxygen Partial Pressure Nominal Composition Differential Thermal Analysis Curve Disproportionation Reaction High Oxygen Partial Pressure
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- N. Kijima, H. Endo, J. Tsuchiya, A. Sumiyama, M. Mizuno and Y. Oguri: Jpn. J. Appl. Phys. 27 (1988) L82l.Google Scholar
- K.Kitazawa, S. Yaegashi, K. Kishio, T. Hasegawa, N. Kanazawa, K. Park and K. Fueki: Adv. Ceram. Mater. (in press)Google Scholar
- H. Endo, J. Tsuchiya, N. Kijima, A. Sumiyama, M. Mizuno and Y. Oguri: submitted to Jpn. J. Appl. Phys.Google Scholar