Radiation stability of gadolinium zirconate: A waste form for plutonium disposition

Zirconate and titanate pyrochlores were subjected to 1 MeV of Kr₊irradiation. Pyrochlores in the Gd₂(Zr_xTi_1-x)2O₇system (x= 0, 0.25, 0.5, 0.75, 1) showed a systematic change in the susceptibility to radiation-induced amorphization with increasing Zr content. Gd₂Ti₂O₇amorphized at relatively low dose (0.2 displacement per atom at room temperature), and the critical temperature for amorphization was 1100 K. With increasing zirconium content, the pyrochlores became increasingly radiation resistant, as demonstrated by the increasing dose and decreasing critical temperature for amorphization. Pyrochlores highly-enriched in Zr (Gd₂Zr₂O₇, Gd₂Zr_1.8Mg_0.2O_6.8, Gd_1.9Sr_0.1Zr_1.9Mg_0.1O_6.85, and Gd_1.9Sr_0.1Zr_1.8Mg_0.2O_6.75) could not be amorphized, even at temperature as low as 25 K.