Influence of Packing Atmosphere on the Microstructures and Transport Properties of Bi-2223/AgAu Tapes
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Oxygen partial pressure was the key factor to tune the phase evolution mechanism of Bi-2223 system. In order to investigate the influence of packing atmosphere on the phase formation rate of Bi-2223, microstructures‚ and the current capacity of final tapes‚ 37-filamentary Bi-2223/AgAu tapes were fabricated by powder-in-tube (PIT) process, and the powder packing process operated in the glove box under different atmosphere of pure O2‚ air, and N2–7.5%O2, with the oxygen partial pressure of 100%‚ 25%, and 7.5%, respectively. With different packing atmosphere, the phase formation rate of Bi-2223 increased obviously during the first heat treatment process (HT1). While, based on the same HT1 process, the maximum Bi-2223 phase content was obtained in the tapes with packing atmosphere of N2–7.5%O2‚ which should be attributed to the suitable Bi-2223 content and distribution. Due to the improvement of superconducting phase content and better texture structure, the critical current density increased with decreasing oxygen partial pressure of packing atmosphere and the maximum value of 19.9 kA/cm2 was reached. Moreover‚ the in-field current capacities of these Bi-2223/AgAu tapes have also been enhanced with low oxygen partial pressure in packing atmosphere, attributed to the improvements of intergrain connectivity.
KeywordsBi-2223/AgAu tapes Packing atmosphere Phase formation rate Microstructure Critical current density
This study was financially supported by the National Key Project of Magneto-Constrained Fusion Energy Development Program under Grant 2015GB115001, National Natural Science Foundation of China under contract No. 51472206, and National Key Research and Development Program 2017YFB0902303.
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