Fabrication and microstructural control of high current ReBa/sub 2/Cu/sub 3/O/sub 7/ current leads (Re=Y, Nd, Sm)

The potential of YBCO superconductors for the development of current leads has been hindered by the difficulties in the fabrication of long single domain bars which exhibit much higher the critical current density than that for the BSCCO counterpart. In this work we report that very long single domain (10 cm/spl times/0.4 cm) self sustained vertical bars can be directionally solidified by using additives such as CeO/sub 2/. The influence of the processing rate has been investigated and we show that current leads which are able to carry a current higher than 2500 A can be fabricated. Quality factors of these bars such as homogeneity, critical current, thermal conductivity and resistance of ohmic contacts are evaluated. At the same time we report the growth conditions of long bars of ReBa/sub 2/Cu/sub 3/O/sub 7/ (Re=Nd, Sm) in air and we investigate the relationship between microstructure and superconducting properties.