A case for oxygen deficiency in Gd2Ti2−xZrxO7 pyrochlore-type oxides

• Gd2Ti2−xZrxO7 pyrochlore-type oxides were studied by XANES.
• The materials were observed to be slightly oxygen deficient.
• The number of oxygen defects present increases with greater Zr incorporation.
• The oxygen defects are charge balanced by the reduction of some Ti4+ to Ti3+.

Pyrochlore-type oxides having the formula Gd2Ti2−xZrxO7 have been studied in the past as potential candidates for the sequestration of nuclear waste elements owing to their chemical robustness and increased resistance to radiation induced damage with greater Zr incorporation. To be used for nuclear waste sequestration applications, all aspects of these materials need to be understood. This is especially the case for the stoichiometry of the materials and the effect of crystal defects. X-ray absorption near-edge spectroscopy (XANES) has been used here to study the local chemical environment of the metal atoms depending on composition. Analysis of Ti K-edge XANES spectra has shown that Gd2Ti2−xZrxO7 (0 ⩽ x < 2) can be slightly O-deficient, and that the level of O-deficiency increases with greater Zr incorporation.