Fracture toughness behavior of the YBa2Cu3O7−x superconducting ceramic with silver oxide additions

Abstract

The influence of silver oxide additions on the fracture behavior of YBa₂Cu₃O_7−x superconducting ceramic was studied. The K_IC value has been found to increase from about 1 MPa√m to as much as 2.4 MPa√m with the blending of 30 wt.% Ag₂O with the 1‐2‐3 powder. All compositions exhibited increasing resistance to fracture with crack extension. The addition of silver to the monolithic sintered structure not only raises the level of the K_R curve, consistent with the rise in K_IC, but also increases dK_R/dΔa, indicative of an improvement in the cumulative toughening efficiency. Microstructural studies implicated crack face bridging by both the 1‐2‐3 grains, as well as the Ag component, as a major contribution to the observed improvement in toughening. The superconducting properties of these composites were not adversely affected by additions of up to 20% Ag₂O.