METHOD OF PREPARING BISMUTH OXIDE SUPERCONDUCTING WIRE

摘要

Powder of not more than 1 mu m in mean particle diameter is prepared to contain a mixture of superconducting phases mainly composed of 2212 phases of Bi-Sr-Ca-Cu or (Bi, Pb)-Sr-Ca-Cu and non-superconducting phases which is obtained by calcining and pulverizing raw material powder at least once, this powder is heat treated at a high temperature and thereafter coated with a metal to prepare a round wire by deformation processing, thereafter a tape type or flat type wire is prepared by deformation processing, then the wire is heat treated under conditions for allowing phase transformation of the 2212 phases of main superconducting phases to 2223 phases with facilitation of grain growth, thereafter the as-formed 2223 phases are highly densified by deformation processing or pressurization, and the wire is again heat treated so that the 2223 phases are strongly bonded with each other and the non-superconducting phases are finely dispersed. Thus, a bismuth oxide superconducting wire having a high critical current density is obtained.