Insight into the order-disorder transition of irradiated pyrochlore solid solutions as potential nuclear waste forms
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European Association of Geochemistry and the Geochemical Society (Goldschmidt)
Pyrochlores (A2B2O7), a common mineral that can uptake large quantities of actinides, are studied as potential nuclear waste forms to immobilize radionuclides. Many have studied pyrochlore solid solutions where different cations on the A or B site are mixed to imitate waste loading of e.g. Pu within the pyrochlore structure. As a response to irradiation or self-irradiation, zirconate (B=Zr) pyrochlores are known to undergo an order/disorder phase transition into a disordered defect fluorite structure while titanate (B=Ti) pyrochlores become amorphous, however the dominating factor towards phase transition of each is unclear in a solid solution. To gain insight into order-disorder processes, the stress and strain of Nd2Zr2O7 and Er2Ti2O7 endmembers and a (ErNd)2(TiZr)2O7 solid solution were examined. Prior and upon irradiation Nd2Zr2O7 and Er2Ti2O7 both showed no strain. With regards to (ErNd)2(TiZr)2O7, it appears that the synthesis method employed was not sufficient to achieve a 50:50 ratio of A and B cations according to the diffraction results. However, the solid solution contained strain while Nd2Zr2O7 and Er2Ti2O7 was strain free. Further synthesis approaches of (ErNd)2(TiZr)2O7 solid solution members are under way to understand the irradiation response of such mixed A and B site pyrochlores.
Pyrochlore, Radioactive wastes, Radionuclides, Order-disorder transformations, Fluorite, Stresses, Neutron diffraction
Chang, S., Thorogood, G. J., Avdeev, M., Brandt, F., Bosbach, D., Ionescu, M., Simeone, D. & Finkeldei, S. C. (2021). Insight into the order-disorder transition of irradiated pyrochlore solid solutions as potential nuclear waste forms. Paper presented at Goldschmidt 2021 Virtual, 4-9 July 2021. Retrieved from: https://2021.goldschmidt.info/goldschmidt/2021/meetingapp.cgi/Paper/8040