Melt-processed REBaCuO (RE: rare earth) superconductors have a high J c at 77 K and a high magnetic field, which are expected to be used for high field applications such as superconducting permanent magnets with liquid nitrogen refrigeration, flywheels, current leads and so on. Mechanical properties such as flexural strength, fracture toughness and ductility are very crucial as well as the superconducting properties: T c , J c , and H irr for industrial applications of high-T c oxide superconductors. However, oxide superconductors have the intrinsic brittleness of the perovskite structure, thus, the strength and the fracture toughness of REBaCuO superconductors have been reported to be low and anisotropic. Therefore, we should investigate and improve mechanical properties to achieve structural reliability for applications.
Large single domain of melt-processed REBaCuO (Dy-123) superconductors with Dy 2 BaCuO 5 (Dy-211) particles and Ag 2 O of 10 wt% was fabricated with a seeding and temperature gradient method in air. In this study, we discuss mechanical properties such as the hardness and the surface roughness, and the flexural strength of the RE-123 bulk, measured at RT. The results of Vickers hardness, surface roughness and the flexural strength showed very important information for evaluating characteristics of RE-123 bulks.