YBCO — monoliths with trapped fields more than 14 T and peak effect

This paper reports on the trapped fields of 14.3 and 11.4 T measured in the gap between two YBCO cylinders and on top of a single YBCO cylinder, respectively. The magnetic flux has been trapped at 17 and 22 K, respectively. The composite material consists of a YBCO-matrix with Ag inclusions and was reinforced by a bandage of steel. A modified melt crystallisation process was applied to grow the bulk superconductors which takes into account the features in the phase diagram due to the additional silver component. On the other hand, the trapped fields at 77 K benefit from the newly proposed chemical doping by Zn on Cu plane sites which results in a well pronounced peak effect near 3 T. This peak in relatively high fields is thought to result from pair breaking by induced magnetic moments due to in plane substitution of Cu by Zn. Thus, more than 1.1 T has efficiently been trapped in a cylindrical sample of only 25 mm in diameter.