Cation antisite disorder in uranium-doped gadolinium zirconate pyrochlores

摘要

The incorporation of uranium into gadolinium zirconate (Gd_2Zr_2O_7) is investigated by synchrotron X-ray powder diffraction and X-ray absorption near-edge structure (XANES) spectroscopy. The results suggest that the uranium cation is largely located on the pyrochlore B-site instead of the targeted A-site. Cation disorder in Gd_2Zr_2O_7 and U-doped Gd_2Zr_2O_7 is investigated by positron annihilation lifetime spectroscopy (PALS) which demonstrates the absence of cation vacancies in these systems. This work provides direct evidence for cation antisite (A- and B-site mixing) disorder in U-doped and off-stoichiometric Gd_2Zr_2O_7 pyrochlore.