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 C. At ambient temperature it has an anion-deficient fluorite related β'-type structure with ordered anion vacancies (space group R anti 3 a = 9.5611 Aa, c = 17.5020 Aa). 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 ∝ 1050 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. (orig.)