Abstract
Understanding and predicting radiation damage evolution in complex materials is crucial for developing next-generation nuclear energy sources. Here, using a combination of ion beam irradiation, transmission electron microscopy and X-ray diffraction, we show that, contrary to the behaviour observed in pyrochlores, the amorphization resistance of spinel compounds correlates directly with the energy to disorder the structure. Using a combination of atomistic simulation techniques, we ascribe this behaviour to structural defects on the cation sublattice that are present in spinel but not in pyrochlore. Specifically, because of these structural defects, there are kinetic pathways for the relaxation of disorder in spinel that are absent in pyrochlore. This leads to a direct correlation between amorphization resistance and disordering energetics in spinel, the opposite of that observed in pyrochlores. These results provide new insight into the origins of amorphization resistance in complex oxides beyond fluorite derivatives.
Highlights
Understanding and predicting radiation damage evolution in complex materials is crucial for developing next-generation nuclear energy sources
The original work connecting amorphization resistance to cation disordering energetics in pyrochlore relied on empirical potentials to establish that correlation[4,5], the physical trends identified have been validated using density functional theory (DFT) calculations, which have examined both the energetics to create antisite pairs[7,8] and to fully disorder pyrochlore to form disordered fluorite[7,8,9]
An even better predictor of amorphization resistance is the gap in energy between the disordered state and the amorphous state, which is qualitatively indicated by the extent of stability of the disordered phase in the phase diagram[5]
Summary
Understanding and predicting radiation damage evolution in complex materials is crucial for developing next-generation nuclear energy sources. The disordering energy, not as fundamental as the nature of the bond, is a more convenient measure as it can be estimated from the phase diagram[5] and can be readily calculated[8,9] This correlation between higher energetics for cation disorder and ease of amorphization has been observed in other materials, including other fluorite derivatives[5,15,16] and even ordered intermetallics[17,18,19,20], where the correlation has received significant attention. It is such a strong indicator of amorphization susceptibility for the titanate pyrochlores as, in those systems, the pyrochlore stabilty field extends to the melting temperature
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