Phase transformation and radiation resistance of B-site high entropy pyrochlores

Two high entropy pyrochlores (HEPs), Gd2(Ti0.2Zr0.2Sn0.2Hf0.2Ta0.2)2O7 and Gd2(Ti0.2Zr0.2Sn0.2Hf0.2Nb0.2)2O7 have been synthesized and irradiated with 800 keV Kr2+ ions and examined by in situ transmission electron microscopy (TEM). The irradiation-induced order-to-disorder phase transformation from pyrochlore to the fluorite structure in these two HEPs and Gd2Sn2O7 was observed by using selected area electron diffraction (SAED), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), and energy dispersive spectroscopy (EDS) mapping. The cation antisite defect (CAD) formation energy and the electron localization function (ELF) were calculated using density functional theory (DFT). Both the experimental results and calculated results suggest that the HEPs exhibit a higher resistance to phase transformation and amorphization than Gd2Sn2O7.