Local structure and oxygen ion dynamics in La doped ceria: 17O NMR study

The local order and oxygen dynamics in La doped ceria (LDC) has been studied by O-17 NMR techniques. High resolution O-17 MAS NMR spectra show several oxygen resonances which are assigned to the lattice sites with 0, 1 and 2 nearest neighbor (nn) La3+ ions. The site with 1 nn La contributes two different lines depending on the presence or absence of oxygen vacancy. The sites with 2 nn La ions are represented by one single line, which indicates that two neighboring La3+ ions always bind one vacancy. Spin-lattice relaxation (T-1) measurements on static samples were carried out between 293 K and 1073 K. The temperature dependence of T-1 has been interpreted assuming two independent relaxation paths. The relaxation below 600 K is assigned to the oxygen dynamics in the lattice without involving vacancy diffusion. The relaxation at a higher temperature is interpreted to be caused by the oxygen hopping between vacant and occupied sites. (C) 2010 Elsevier B.V. All rights reserved.