Bending mechanical properties of a single-grain Y123 bulk superconductor at liquid nitrogen temperature

In order to investigate the mechanical properties of a single-grain Y123 bulk with 15 wt.% Ag at liquid nitrogen temperature (LNT), three-point bending tests of specimens cut from the bulk were carried out. The dimensions of the bending test specimens were 4 × 3 × 36 mm3. The loading was carried out in the c-axis or perpendicular to it such that the normal stress induced by loading was perpendicular to the c-axis. Young's modulus at LNT by loading in the c-axis and perpendicular to it were 143 and 134 GPa and the bending strengths were 115 and 128 MPa, respectively. These bending strength values were higher than those at room temperature (RT) for this bulk. From the comparison with the other rare earth element based bulks, the smaller the ionic radius of Y or rare earth elements, the higher Young's modulus and the bending strength of the bulks. This implies that the strength is basically controlled by the ideal crystal strength of bulks, irrespective of the crystal orientation and, further, defect induced during fabrication process, so long as the defect size is comparable. The step-wise undulation in the crack propagation direction on the fracture surfaces by loading in the c-axis was significant as compared with that by loading in perpendicular to it.