NEUTRON AND RAMAN-SCATTERING STUDIES OF SURFACE-ADSORBED MOLECULAR VIBRATIONS AND BULK PHONONS IN ZRO2 NANOPARTICLES

Inelastic neutron-scattering method (neutron spectroscopy) was applied to the study of the phonon densities of states of zirconia nanopartic les, the O-H stretch vibrations of physisorbed water molecules and che misorbed hydroxyl groups on the surface. Raman scattering was also use d to measure the zone-center phonon modes. The observed distinct phono n frequencies and band widths at 10-120 meV reflect the different crys talline symmetries and compositional fluctuations in the small grain a nd interfacial regions of monoclinic ZrO2, tetragonal or mixed cubic a nd tetragonal rare-earth-modified zirconia. The observed neutron spect ra for pure ZrO2, Ce0.1Zr0.9O2 and Nd0.1Zr0.9O1.95 display a band cons isting of peaks at 26, 30, and 40 meV and a broad band extending from 50 to 100 meV, The O-H bonds in surface hydroxyl groups and water on t hese zirconias result in the different frequencies of the O-H stretch vibrations at 400-600 meV. (C) 1997 Elsevier Science B.V.