查看文章

Neutron diffraction and total scattering are combined to investigate a series of single-phase 10-component compositionally complex fluorite-based oxides, [(Pr_0.375Nd_0.375Yb_0.25)₂(Ti_0.5Hf_0.25Zr_0.25)₂O₇]_1-x[(DyHoErNb)O₇]_x, denoted as 10CCFBO_xNb. A long-range order-disorder transition (ODT) occurs at x ​= ​0.81 ​± ​0.01 from the ordered pyrochlore to disordered defect fluorite. In contrast to ternary oxides, this ODT occurs abruptly without an observable two-phase region; moreover, the phase stability in 10CCFBOs deviates from the well-established criteria for simpler oxides. Rietveld refinements of neutron diffraction patterns suggest that this ODT occurs via the migration of oxygen anions from the position 48f to 8a, with a small final jump at the ODT; however, the 8a oxygen occupancy changes gradually (without an observable discontinuous jump). We further discover diffuse scattering in Nb-rich …