Intrinsic Structural Disorder and Radiation Response of Nanocrystalline Gd₂(Ti_0.65Zr_0.35)₂O₇ Pyrochlore

Isometric pyrochlore, A 2 B 2 O 7, has been extensively studied as a phase for the incorporation of actinides because of its use as an inert matrix nuclear fuel and waste form. A critical issue is the effect of cation and anion disordering on the accumulation of radiation damage due to the alpha decay of actinides. The degree of disordering of A- and B-site cations, as well as oxygen vacancies, in nanocrystalline Gd 2 (Ti 0.65 Zr 0.35 ) 2 O 7 pyrochlore was tailored by mechanical milling with subsequent thermal treatments and quantified by X-ray diffraction and Raman spectroscopy. Annealing experiments at 1000 and 1200 °C for different times showed that the nanocrystalline Gd 2 (Ti 0.65 Zr 0.35 ) 2 O 7 displayed a gradual decrease in resistance to radiation-induced amorphization that correlates with the increasing degree of ordering of the cations and anion vacancies, highlighting the effect of disordering on the radiation response of nanocrystalline pyrochlore. These results illustrate that the pyrochlore structure type can be designed to function in high-radiation environments by changing the composition, crystal size, and degree of inherent disordering.