Effect of controlled carbon impurities on J/sub c/ in Ag/Bi(2223) tapes

An extensive study of the detrimental effect of C on critical current densities (J/sub c/) of Ag sheathed Bi(2223) tapes has been carried out. High J/sub c/ ran only be obtained if the C content is kept to a minimum. Successive calcination steps at 820/spl deg/C are effective in reducing the amount of C in the resulting powders. On the other hand, high energy milling increases the amount of C in the powder. Controlled quantities of C impurities were introduced into the powders by performing the calcinations in a CO/sub 2/ rich atmosphere. The J/sub c/ measured on tapes obtained with C-rich precursors are lower by a factor of 2 to 4 than the J/sub c/ of tapes from powders calcined in air.<
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