Critical current densities in Bi-2212 thick films

Abstract

Bi2Sr2CaCu2O8+δ (Bi-2212) films of 130 μm thickness with average critical current densities of 5000 A/cm2 (best value 6200 A/cm2) at 77 K/0 T were produced via tape casting and partial melting. This corresponds to a current carrying capacity of 65 A/cm. The critical current densities (jc) depend strongly on the conditions of the partial melting process (temperature, p(O2) and can be significantly increased by additional post-partial melting heat treatments. Controlling the maximum temperature at 5–8°C above the solidus enables one to achieve high critical current densities, but only slow cooling with 5 K/h from the maximum temperature down to 850°C and isothermal annealing for 70 h at 850°C resulted in the highest jc's. The improvements of the critical current densities are accompanied by microstructural changes caused by the different heat treatment steps.