Raman scattering study of the anharmonic effects inCeO2−y nanocrystals

Abstract

We have studied the temperature dependence of theF2g Raman mode phonon frequency and broadening inCeO2−y nanocrystals. The phonon softening and phonon linewidth are calculated using a modelwhich takes into account the three-and four-phonon anharmonic processes. A detailedcomparison of the experimental data with theoretical calculations revealed the predominanceof four-phonon anharmonic processes in the temperature dependence of the phonon energyand broadening of the nanocrystals. On the other hand, three-phonon processes dominatethe temperature behavior of phonons in polycrystalline samples. The anti-Stokes/Stokespeak intensity ratio was also investigated and found to be smaller for nanosizedCeO2 powders than in the bulk counterpart.