Phonon–phonon interactions in Ce_0.85Gd_0.15O_2−δ nanocrystals studied by Raman spectroscopy

Abstract

Abstract Phonon–phonon interactions and phase stability of Gd‐doped ceria nanocrystals were examined over the temperature range 293–1100 K by Raman spectroscopy. The phonon confinement model (PCM) based on size, inhomogeneous strain and anharmonic effects was used to properly describe the anharmonic interactions in this system. The interplay between size and anharmonic effects influenced different phonon decay channels in nano grains than in larger grains. After the gradual cooling down to room temperature (RT), the Raman study revealed the phase separation in this system pointing to the phase instability of Ce 0.85 Gd 0.15 O 2−δ nanocrystals after heat treatment. The concentration of extrinsic (intrinsic) oxygen vacancies was also studied by Raman spectroscopy during the heat treatment of the Ce 0.85 Gd 0.15 O 2−δ nanocrystalline sample. Copyright © 2009 John Wiley & Sons, Ltd.