PREPARATION AND CRITICAL CURRENT-DENSITY OF MELT-PROCESSED Y-BA-CU-O THICK-FILMS AND AGPD-SHEATHED TAPES

Thermal analysis by differential scanning calorimetry (DSC) has shown that melting of YBa2CU3Ox is completed at 1000-1010-degrees-C in a nitrogen atmosphere. The N2 can be exchanged by 02 without solidification of the melt and the solidification starts in O2 below 1000-degrees-C in the supercooled melt. Applying such a thermal treatment to YBa2Cu3Ox thick films on AgPd20 ribbons a partial alignment of the c axis normal to the large plane of the films can be achieved. The textured films exhibit a strong anisotropy of the critical current density and of the irreversibility field and an improved weak link behaviour compared with that of untextured samples. A maximum J(c) value of 1450 A cm-2 at 77 K in zero field was measured. For AgPd-sheathed tapes produced by the 'powder-in-tube' method, sintering in a nitrogen atmosphere before the heat treatment in oxygen results in high values of J(c), up to 5950 A cm-2 (77 K, 0 T).