Fracture toughness of radiation-damaged zircon studied by nanoindentation pillar-splitting

Nanoindentation micro-pillar splitting was employed to measure the fracture toughness (KC) of growth-zones in radiation-damaged zircon with varying degrees of disorder (∼45%-80% amorphous fraction). The radiation-induced amorphization is caused by α-decay events from incorporated U and Th (∼0.22-0.43 wt. % UO2 and ∼0.02-0.08 wt. % ThO2). KC has been found to increase with the increase in the amorphous fraction (∼2.39 to 3.15 MPa*m1/2). There is a good correlation with the modulus/hardness (E/H) ratio evolution over the investigated zones. As zircon has been proposed as a nuclear waste form for the incorporation and disposal of Pu, a deeper knowledge of KC as a function of radiation damage is important, as radiation-induced cracking provides diffusion paths for the release of incorporated actinides. Zoned zircon provides a model for the development of multilayer coatings and complex ceramics that can be designed to be resistant to crack propagation.