Improvement of J_c of Thick Bi-2212 Film Spray-painted on an Ag Substrate

Abstract

Thick Bi₂Sr₂CaCu₂O_x(Bi-2212) films prepared by partial melting is widely used with cables, magnetic shields, etc. as their critical current density (J_c) is very high. The samples were prepared by spraying Bi-2212 paste on Ag substrata, and then by partially melting these to the thickness of 50 μm. During production, optimum atmospheric pressure, heat treatment, cooling speed and annealing time had to be applied to obtain high J_c values and critical temperature. As the best condition for heating the samples in optimum oxygen concentration, the samples were melted for 600 s at 1163 K in oxygen, and then cooled by the rate of 0.2 K/min. The highest J_c so far was obtained with these samples and T_c also increased to 91 K. When the sample was heat treated for 54 ks at 773 K in nitrogen, J_c improved to 120 A/mm² at 77 K and 0 T.