Phase formation in high-Tc Bi-2223 silver-sheathed tapes for power cables

The main manufacturing problem associated with powder-in-tube (PIT) methods is the complex phase equilibria of the bismuth cuprate system in which a multitude of solidus and liquid phases may coexist at the processing temperature. Such knowledge is important for improving the current performance of tapes for their use in superconducting applications. The elucidation of the phase equilibria in the ceramic core and especially at the silver interface is vital if high-critical-current density (J_c) tapes are to be manufactured. Transport and structural measurements have been used by carefully controlling and systematically changing the annealing temperature and time, we have been able to ascertain the complex phase equilibria and show future improvement for operation at 77 K.