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

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Abstract
The influence of silver oxide additions on the fracture behavior of YBa2Cu3O7−x superconducting ceramic was studied. The KIC 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 KR curve, consistent with the rise in KIC, but also increases dKR/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.