A STUDY OF BUBBLE-DEFECT FORMATIONS IN AG SHEATHED BI2SR2CACU2O8-2212) SUPERCONDUCTING TAPES(X (BI)

Bubble-defect formations were studied in Ag sheathed similar to 60 mu m thick single-filamentary Bi2Sr2CaCu2O8+x (Bi-2212) oxide-powder-in-t ube (OPIT) conductors. Bubble defects were affected by the powder-proc essing method, spray-roasted (SR) or solid-state (SS) and annealing co nditions, removing or not removing the rolling lubrication, exposing p recursor powder to air, and ball-milling. The effect of powder carbon content on bubbling was studied for SR powder (370-4010 ppmw) and SS p owder (220-590 ppmw). It was possible to eliminate bubbles using SS po wder, appropriate pre-annealing conditions, and processing in air for a wide range of processing conditions and conductor lengths (up to 90 m). The method of eliminating bubble defects in SS powder tapes was al so compatible with high critical current density (J(c)) processing.