Influence of calcination atmosphere on the phase evolution mechanism of Bi-2223 high temperature superconductor

摘要

Precursor powders of Bi_2Sr_2Ca_2Cu_3O_(10+δ) (Bi-2223) high temperature superconducting tapes were prepared with spray pyrolysis technique. By tuning the oxygen partial pressure in calcination atmosphere as 1.0%, 7.5%, and 10.0%, respectively, the influences of calcination atmosphere on the phase evolution dynamics during the precursor powders calcination process have been discussed. Then the optimal calcination temperatures have been obtained correspondingly. Moreover, Bi-2223 multi-filament tapes have been fabricated with the precursor powders calcinated under different atmosphere. The effects of precursor powder calcination parameters on the phase composition, microstructures as well as the current capacity of final tapes have been systematically studied. Due to the proper secondary phase content and enhanced Bi-2223 texture structures, the maximum critical current of 109 A at 77 K, self-field, corresponding to the critical current density of 23.3 kA cm~(-2) has been obtained with the oxygen partial pressure of 7.5% in calcination atmosphere and the calcination temperature of 790 °C.