Effects of intermediate deformation and thermal processing in the OPIT process upon critical current density of Ag/BiSSCO tapes

Abstract

Critical current density, J/sub c/, of Ag/Bi(Pb)SCCO tapes in as-deformed and as-sintered states were studied at different stages of tape processing. Intermediate pressing and rolling result in significant I/sub c/ degradation. Non-zero I/sub c/ remains after the applications of pressing load up to 11 and 8 GPa following the third and first sintering, respectively. Under rolling conditions I/sub c/ remains non-zero up to maximum tape thickness reduction of 20%. Bending tests show that I/sub c/ reduction is the result of deformation-induced micro-crack formation which are easily healed during the first hour of the next sintering. Intermediate deformation after the first sintering cycle has been shown to accelerate significantly the 2212 to 2223 phase transformation during the first hours of the second sintering step. I/sub c/ growth during the first hour of the second sintering cycle is not connected with that phase transformation and is presumed to be the result of pinning ability and structure connectivity enhancement.