X-Ray diffraction study of oxygen deficient Y$_2$Ti$_2$O$_{7-\delta}$ pyrochlore powders synthesized by high-energy ball milling (HEBM)

International audienceY$_2$Ti$_2$O$_7$ pyrochlore are widely used for various applications, from oxygen transport to materials strengthening. Ultra-pure oxygen deficient Y$_2$Ti$_2$O$_{7-\delta}$ pyrochlore powders synthesized by high-energy ball milling (HEBM) are studied by X-ray diffraction (XRD). Rietveld analysis of diffraction patterns reveals that a large oxygen sub-stoichiometry can be accommodated in this material with only minor structural changes. This accommodation results from the ability of Ti ions to change their valence state, which is confirmed by complementary EELS analysis. It may also explain why Y$_2$Ti$_2$O$_7$ is both radiation and mechanical milling resistant. This work highlights the fact that selection of cations allows rigid ionic structures like pyrochlore to accommodate a large amount of point defects