CRITICAL-CURRENT DENSITIES IN BI-2212 THICK-FILMS

Bi2Sr2CaCu2O8+delta (Bi-2212) films of 130 mu m thickness with average critical current densities of 5000 A/cm(2) (best value 6200 A/cm(2)) at 77 K/0 T were produced via tape casting and partial melting. This c orresponds to a current carrying capacity of 65 A/cm. The critical cur rent densities (j(c)) depend strongly on the conditions of the partial melting process (temperature, p(O-2)) and can be significantly increa sed by additional post-partial melting heat treatments. Controlling th e maximum temperature at 5-8 degrees C above the solidus enables one t o achieve high critical current densities, but only slow cooling with 5 K/h from the maximum temperature down to 850 degrees C and isotherma l annealing for 70 h at 850 degrees C resulted in the highest j(c)'s. The improvements of the critical current densities are accompanied by microstructural changes caused by the different heat treatment steps.