Effects of Ag addition in Bi-2223 bulk using current leads

To apply a high-Tc superconductor for a current lead, improvements of critical current density(Jc) and contact resistance(Rc) are very important. We have been studying the effect of Ag addition on Bi-2223 bulk fabricated by the cold isostatic pressing and sintering process. Addition of 5 wt.%, Ag resulted in an increase in Jc value from 500 to 800 A/cm/sup 2/ and in a decrease in Rc value from 10/sup -6/ to 10/sup -7/ /spl Omega/cm/sup 2/ at 77 K, 0 T. These improvements were due to both an increase in size of Bi-2223 grains and increased density of the sintered bulk. We also measured the integral of heat conduction between 77 K and 4.2 K. The integral of heat conduction in a 5 wt.% Ag added specimen was estimated to be 80 W/m on an equality with that of a specimen without Ag. These results indicate that Ag addition did not affect the thermal conductivity since the Ag particles dispersed homogeneously in the sintered Bi-2223 hulk. Furthermore, as a result of improvement in the process, we obtained a maximum Jc value of 2500 A/cm/sup 2/ and Ic value of 1150 A at 77 K, 0 T in a 5 wt.% Ag added pipe-shaped specimen.<
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