Solid state NMR investigation of oxygen dynamics in scandium doped ceria in 50 K to 1073 K temperature range

In this work we investigate the solubility of scandium in ceria, and present a detailed investigation of oxygen dynamics in 0.5% scandium doped ceria from 50 K to 1073 K by 45Sc solid state NMR line shape, chemical shift, and spin-lattice relaxation analysis. We show that oxygen vacancy is strongly attached to the scandium in the seven-coordinated scandiumaoxygen vacancy complex (7-Sc), but even at room temperature the vacancy is moving freely around the scandium atom between eight equivalent sites in millisecond time scale. The activation energy of that vacancy jump is 0.37 eV. The eight-coordinated (8-Sc) scandium ion retains cubic environment down to 50 K. The exchange rate between 7-Sc and 8-Sc sites exceeds 103 Hz above T > 600 K.