Alpha-decay-induced amorphization in complex silicate structures

Alpha decay in Cm-doped Ca[sub 2]Nd[sub 8](SiO[sub 4])[sub 6]O[sub 2], Pu-doped ZrSiO[sub 4], and natural ZrSiO[sub 4] minerals results in the simultaneous accumulation of point defects and amorphous regions that both contribute to the macroscopic swelling. A composite model for the macroscopic swelling is used to determine the amorphous fraction as a function of cumulative alpha-decay events. The dependence of the derived amorphous fraction in Ca[sub 2]Nd[sub 8](SiO[sub 4])[sub 6]O[sub 2] on cumulative alpha-decay events is consistent with amorphization occurring directly within an individual displacement cascade. In ZrSiO[sub 4], on the other hand, the rate of amorphization is lower and the derived amorphous fraction as a function of cumulative alpha-decay events is consistent with models for amorphization occurring as a result of the local accumulation of high-defect concentrations from the multiple overlapping of displacement cascades.

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