Levitation forces and mechanical properties of VGF melt-textured YBCO

Thermal cycling reduces the levitation force of melt-textured YBCO. Investigations of the mechanical properties reveal that the fracture toughness, K/sub IC/, and the hardness, H/sub v/, are very low. K/sub IC/ decreases even more after thermal cycling. These poor mechanical properties in combination with nearly no possibility for stress relief due to plastic deformation are thought to be responsible for the generation and propagation of cracks. These cracks reduce the effective radii of the screening currents leading to a decreased magnetic moment and the observed reduction of the levitation force.