Fabrication and Superconducting Properties of Bi2Sr2CaCu2Oy Multilayer Tape Prepared by Continuous Heat Treatment

Flexible Bi-2212 multilayer tapes of ∼80 m length were prepared by a combination of the oxide-painting method and the continuous heat-treatment technique. The tapes were heat-treated by passing them through a tube furnace having temperature gradient which induced partial melting and slow cooling. The tapes had critical current density (J c) values higher than 1× 105 A/cm2 at 4.2 K and 12 T. The tapes showed excellent J c vs strain properties. J c was almost constant up to the bending strain of 0.7% (the bending diameter of 30 mm). Hence the “react & wind” technique could be applied to the fabrication of coils. A small pancake coil fabricated by the “react & wind” technique had J c values almost equal to those of short straight tapes.