Study of inhomogeneous distribution of Bi-2223 phase in Ag/Ni composite-sheathed tapes

Inhomogeneous distribution of Bi-2223 ceramics in Ag/Ni composite-sheathed superconducting tapes was studied systematically. Difference of volume fractions of Bi-2223 phase in different locations at the sheath–ceramic interface was reported first. The real local oxygen partial pressure (PO2) variance was identified as the reason leading to the phenomenon. Meanwhile, the volume fraction evolution of Bi-2223 phase in different locations of samples treated in various PO2 with sintering time extension was studied. It was concluded that a long-time sintering in a PO2 reduced atmosphere seemed to be good for decreasing inhomogeneous distribution of Bi-2223 ceramics. In addition, a combined heat treatment in the initial formation stage of Bi-2223 phase was designed to successfully eliminate the inhomogeneous distribution of Bi-2223 ceramics.