The peritectic transition of a Bi-2223 superconductor with a nominal composition of Bi1.7Pb0.3Ca2.4Sr1.6Cu3.6Oy was studied kinetically under different atmospheres and temperature gradients. It was interesting to find that both the peritectic transition and reaction were dependent on the ambient atmosphere. With a nitrogen flow rate of 25 mL/min, the incongruent melting point obtained was increased with heating rates. The peritectic points, Tp, extrapolated to 0 °C/min gradient from the onset and the peak positions of the DSC curves were 794 and 818 °C, respectively. Average ΔHfus integrated from the endothermic DSC peaks was 140 ± 7 kJ/mol with an activation energy of 547 kJ/mol. A weight loss corresponding to 1.6 mol O-atom was observed from the Tp reaction for 1 mol of Bi-2223 superconductor. Under the oxygen atmosphere, the peritectic point obtained from the peak positions was 887 °C and ΔHfus = 67 ± 7 kJ/mol with only 20% O-atom decomposed compared to that under the nitrogen atmosphere. The dTp/d(log O2%) was (21.3±0.6) °C. Thermal stability of Bi-2223 was greatly enhanced under the oxygen atmosphere.
關聯:
Physica C: Superconductivity and its Applications 235-240(PART 1), pp.323-324
