Beschreibung:
<jats:p>A new hierarchical approach is presented for elucidating the structural disorder in Ce<jats:sub>1−<jats:italic>x</jats:italic></jats:sub>Gd<jats:sub><jats:italic>x</jats:italic></jats:sub>O<jats:sub>2−<jats:italic>x</jats:italic>/2</jats:sub>solid solutions on different scale lengths. The primary goal of this investigation is to shed light on the relations between the short-range and the average structure of these materials<jats:italic>via</jats:italic>an analysis of disorder on the mesocopic scale. Real-space (pair distribution function) and reciprocal-space (Rietveld refinement and microstructure probing) analysis of X-ray powder diffraction data and electron spin resonance (ESR) investigations were carried out following this approach. On the local scale, Gd- and Ce-rich<jats:italic>droplets</jats:italic>(<jats:italic>i.e.</jats:italic>small regions a few ångströms wide) form, exhibiting either a distorted fluorite (CeO<jats:sub>2</jats:sub>) or a C-type (Gd<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>) structure in the whole compositional range. These droplets can then form C-type nanodomains which, for Gd concentrations<jats:italic>x</jats:italic><jats:sub>Gd</jats:sub>≤ 0.25, are embedded in the fluorite matrix. At the site percolation threshold<jats:italic>p</jats:italic><jats:sub>C</jats:sub>for a cubic lattice (<jats:italic>x</jats:italic><jats:sub>Gd</jats:sub>=<jats:italic>p</jats:italic><jats:sub>C</jats:sub>≃ 0.311), C-type nanodomains percolate inside each crystallite and a structural phase transformation is observed. When this occurs, the peak-to-peak ESR line width Δ<jats:italic>H</jats:italic><jats:sub>pp</jats:sub>shows a step-like behaviour, which can be associated with the increase in Gd–Gd dipolar interactions. A general crystallographic rationale is presented to explain the fluorite-to-C-type phase transformation. The approach shown here could be adopted more generally in the analysis of disorder in other highly doped materials.</jats:p>