The structural evolution of a scandia/nitrogen co-doped zirconia sample, Sc_0.148Zr_0.852O_1.72N_0.14, 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-3, a = 9.5611 Å, c = 17.5020 Å). 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.