PROPERTIES OF LARGE-SCALE MELT-PROCESSED YBCO SAMPLES

Magnetic bearings and superconducting permanent magnets are some of the first possible applications of bulk high T(c) superconductors. Large samples were prepared by a new melt process starting from reacted YBCO 123 and 21 1 powders. The addition of PtO2 to the mixture led to reduced 21 1 inclusion size and better homogeneity. Simultaneously the density of microcracks dividing the a - b basal plane was reduced. For testing the overall magnetic properties of these samples magnetization and levitation force measurements were performed. In comparison to samples without PtO2 addition a strong increase in the magnetization M and the repulsion force from a magnet were observed. The maximum in the field dependence of M increased to more than 1000 G. According to the time dependence of the trapped field after a field cooling experiment an acceptable flux creep at 77 K for a long-term application was achieved.