Synchrotron X-ray diffraction study of nanostructured Er2O3-TiO2 (50–60 mol % Er2O3) solid solutions

Abstract

Monochromatic synchrotron X-ray diffraction data demonstrate that single-crystal and polycrystalline xEr2O3 · (1 − x)TiO2 (x = 0.5–0.6) solid solutions consist of a fluorite-like disordered (Fm3m) phase and a nanoscale (40–1000 nm) pyrochlore-like ordered phase (Fd3m) of the same composition in the range 0.5 ≤ x ≤ 0.57, coherent with the disordered phase. Reducing the density of structural defects in the unit cell of Er3TiO6.5 (x = 0.6) leads to a structural transformation of the pyrochlore-like phase into a Ta2O3-type ordered phase (Ia3), derived from the fluorite phase. In the composition range of the solid solutions (0.5 < x < 0.6), the lattice parameter of the fluorite-like phase follows Vegard’s law. The formation of nanodomains with different degrees of order is shown to be caused by the internal strain due to the high density of structural defects in their unit cells.