Fracture strength properties of (Gd,Y)BaCuO large single-grain bulk at liquid nitrogen temperature

Abstract

In order to investigate the fracture strength properties of a (Gd,Y)BaCuO large single-grain bulk with 90 mm in diameter, bending tests were carried out at liquid nitrogen temperature 77 K for the specimens cut from the bulk sample. The large single-grain bulk was fabricated by RE compositional gradient technique to overcome the problem of undesirable nucleation apart from the seed crystal. One precursor that consisted of some regions with different Gd and Y contents was used for the fabrication. Bending tests for the plain and the V-notched specimens were carried out to evaluate the fracture strength and fracture toughness, respectively. The fracture strength values of the specimens that included the interface between two regions with different Gd and Y contents were not lower than those of the specimens that did not include the interface, which is similar to the bending test results at room temperature. The fracture strength values at 77 K were higher than those at room temperature.