THE EFFECT OF OXYGEN PARTIAL-PRESSURE DURING HEAT-TREATMENT ON THE MICROSTRUCTURE OF DIP-COATED BI-2212 AG AND AG ALLOY TAPES/

The evolution of the microstructure during heat treatment was investig ated for dip-coated Bi2Sr2CaCu2Oy(Bi-2212)/Ag and Ag alloy tapes as a function of temperature and oxygen partial pressure(P-O2=0.01, 0,21 an d 1 atm) using quenched and fully-processed tapes, The microstructures were essentially the same for Bi-2212 on pure Ag and on the Ag alloy, Although the melting temperature of Bi-2212 increased with increasing P-O2, the solidification temperature(T-sol) of Bi-2212 for P-O2=0.21 atm was higher than that for P-O2=1 atm, The volume fraction and grain alignment of Bi-2212 processed in P-O2=0.01 atm was smaller than in t apes processed in 0.21 and 1 atm, which were quite similar. HR-TEM stu dies on grain boundaries and AC susceptibility measurements suggest th at the higher critical current density(J(c)) for tapes processed in P- O2=1 atm than that for 0.21 atm is due to improved coupling of the gra ins.