High-temperature neutron powder diffraction study of scandia/nitrogen co-doped zirconia

The structural evolution of a scandia/nitrogen co-doped zirconia sample, SC0.148Zr0.852O1.72N0.14, was investigated by neutron powder diffraction up to 1700 degrees C. At ambient temperature it has an anion-deficient fluorite related beta'-type structure with ordered anion vacancies (space group R (3) over bar, a = 9.5611 angstrom, c = 17.5020 angstrom). With increasing temperature a gradual transformation into a cubic fluorite-type phase (Fm3m) with randomly distributed vacancies takes place which is accompanied by an enrichment of Sc in the rhombohedral phase and completed at similar to 1050 degrees C. At higher temperatures probability densities and single particle potentials of the anions were determined. The incorporation of nitrogen into the scandia-zirconia material significantly increased the activation energy for anion migration to values above 1 eV. The anions migrate predominantly along the < 100 >-directions to neighbouring sites.