Effect of CaCuO₂ addition to precursors on I_c and I_c-H behaviours of Bi-2223/Ag tapes fabricated by the two-powder process

Precursors prepared by mixing (Bi,Pb)-2212 and CaCuO₂ have been successfully used in the synthesis of high quality Bi-2223/Ag tapes. The effect of excess CaCuO₂, over a range between -5 and 15 at.%, on the properties of monofilamentary Bi-2223/Ag tapes has been studied. It was found that the maximum value of I_c was 23 A at 77 K for a sample doped with 10 at.% CaCuO₂ but that too much doping (e.g. 15 at.% addition) will decrease the I_c of a sample significantly due to a higher level of the impurity phase. However, the observed I_c-H behaviour for tape with 15 at.% CaCuO₂ addition was better than what was observed for undoped samples and for samples with relatively less CaCuO₂ dopant, indicating that excess CaCuO₂ enhanced the flux pinning. Based on the results obtained from monofilamentary samples, 37-filamentary tapes with and without CaCuO₂ addition were fabricated. The I_c of the 5 at.% CaCuO₂-doped sample was 45 A at 77 K, whereas it was 36 A for the undoped sample.