Superconducting Materials for Practical Applications

Different applications of superconductors require different material properties. In this paper a short account is given of the relevant properties of the main materials of interest, BSCCO, MgB2 and YBCO. While BSCCO tapes are well established, the low irreversibility field limits their use at 77K while at 30K where they can stand reasonably high magnetic fields, the cheapness and ease of manufacture of MgB2 makes this new material a serious competitor. Bulk YBCO is also well developed and can produce high fields, but coated YBCO conductors have more applications if the cost can be brought down. AC losses are central to many applications. Since the loss/vol is proportional to Jc, but the volume of material required for a given magnet is inversely proportional to Jc the loss is independent of the material used and depends only on the width of the conductor. However using fine filaments requires that they be decoupled, and is in conflict with the need to avoid high angle grain boundaries across the current p...