Investigation of the Potential Energy Landscape for Vacancy Dynamics in Sc-Doped CeO2

Abstract

Here, we provide a comprehensive picture of the potential energy landscape (PEL) for oxygen-vacancy migration in Sc-doped ceria (SDC) based on the results from a combined application of 45Sc and 17O nuclear magnetic resonance (NMR) and electrochemical impedance spectroscopy (EIS). The oxygen vacancies in SDC perform rapid symmetry-related jumps in the nearest-neighbor coordination shell of Sc traps as well as hopping from one Sc trap to another over length scales of a few nanometers. The activation energies for these two processes are determined to be 0.4 and 1.2 eV, respectively. The depths of these potential wells are modulated via high-frequency elastic deformation of the lattice, with a characteristic activation energy of ∼0.2 eV. The hopping of vacancies between Sc traps control the ionic conduction process in SDC, and the corresponding time scale is identical to the conductivity relaxation time scale.