Mechanical properties of Sm-Ba-Cu-O bulk superconductors at room temperature

In order to investigate the mechanical properties of Sm-Ba-Cu-O bulk superconductors fabricated using TSMG method such that Sm123:Sm211 in molar ratio was 100-Z:Z (Z = 16.7, 28.6), tensile tests in the direction perpendicular to the c-axis have been carried out at room temperature by using the small specimens cut from the bulk samples. Although, non-linear behavior was seen in a few specimens, stress-strain curves were almost linear until the fracture. The non-linear behavior is presumably ascribed to the opening of pre-existing micro-cracks parallel to the c-axis and the slow propagation of them. The Young's modulus for both samples was almost equal. Poisson's ratio based on the transverse strain parallel to the c-axis was smaller than that based on the strain perpendicular to it. One of the possible reasons for it will be the reduced transverse shrinkage by the constraint at the interface between the specimen and the aluminum alloy tensile rod coupled with the opening of the pre-existing micro-cracks perpendicular to the c-axis. Tensile strength for the sample with 28.6 mol% of Sm211 was not higher than that with 16.7 mol%. It is presumably ascribed to the low cohesive force between the Sm211 particles and the matrix. The effect of loading condition with respect to that of the crystal growth on the strength was not clear. No significant difference in the strength was found between the specimens including a growth sector boundary and those without it.