Effect of the Bulk Size During Oxygen Annealing on the Mechanical Properties of Dy-123 High-TC Superconductors

It is known that cracks are formed when bulk superconductors are subjected to the oxygen annealing process, and that cracking is easier in larger bulk materials. Commercial bulk superconductors are subjected to oxygen annealing in a large block state, while the mechanical properties of the superconductors are often evaluated using specimens that are cut from a large pellet and then subjected to the oxygen annealing process. Therefore, it is suspected that there may be some discrepancies in the mechanical properties of these superconducting materials. We conducted bending and tensile tests on various specimen sizes after oxygen annealing. Observations of cracks formed during the oxygen annealing process were made. The cracking behavior was analyzed using a fracture toughness test.