Gd2Zr2O7 ceramics, one of the most promising ceramic waste forms, with a series of grain sizes (55 to 634 nm) were synthesized and irradiated by He ion beam (190 keV) up to a fluence of 5 x 1017 ions/cm2. Using grazing-incidence X-ray diffraction (GIXRD), scanning electron microscope (SEM) and atomic force microscope (AFM) we were able to study the structural degradation and interfacial phenomena as grain size and level of He radiation vary. We found that the structural degradation, such as amorphization, cell volume expansion, lattice distortion, and He bubble formation, appear to be grain size dependent at the same ion fluence. Moreover, the threshold He bubble concentration (at.%) is much higher for nanograin ceramics compared with that of the submicron samples. Further, we carried out high temperature oxide melt solution calorimetry to investigate the energetic landscape as function of grain size and irradiation level. The results highlight the critical role of grain boundary in structural stabilization of Gd2Zr2O7 ceramics, and inhibition of the multi-stage He bubble formation within the grains and at the grain-grain interfaces.

He irradiation-induced structural degradation, interfacial phenomena, and energetic evolution for defect-fluorite Gd2Zr2O7 ceramics

2019 Spring National Meeting

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