Acoustic Vibrations of Monoclinic Zirconia Nanocrystals

Abstract

Polarized low-frequency Raman spectra originating from confined acoustic vibrations are reported for monoclinic ZrO2 nanoparticles with a narrow size distribution synthesized from a continuous supercritical water process. The monoclinic lattice structure is taken into account for the interpretation of the spectra by comparing with isotropic and anisotropic continuum elasticity calculations for monodomain nanocrystals. The various mechanisms leading to the broadening of the Raman peaks are discussed. We demonstrate that an accurate determination of the size distribution of the nanoparticles is possible using the Raman peak due to the fundamental breathing vibration which is hardly broadened by the elastic anisotropy and the shape distribution.

THz nanocrystal acoustic vibrations from ZrO2 3D supercrystals

“…For these reasons we attribute the main band at 40-50 cm À1 to the breathing vibration of the ZrO 2 nanocrystals. It is remarkably sharp when compared to previously reported measurements, 24,25,27 certainly due to the much lower nanocrystal size variation of our samples. The total quality factor Q dened as the ratio of the peak frequency to its full width at half maximum is about 4, which is signicantly higher than most spectra reported in the literature including previous measurements on ZrO 2 nanocrystals.…”

“…The most intense peaks are in the low-frequency range for all the samples investigated in this work, in agreement with previous measurements on ZrO 2 nanocrystals. 24,25 The inset of Fig. 1 shows the ngerprint region of the crystal lattice vibrations for all the samples studied.…”

“…Such peaks have already been reported for ZrO 2 nanocrystals and are therefore expected in our samples. 24,25,27,29 But a careful analysis of the spectra is required in order to assign the lowfrequency peaks to conned vibrations without doubt.…”

Contact laws between nanoparticles: the elasticity of a nanopowder

“…TiO 2 and ZrO 2 nanopowders were prepared with a continuous hydrothermal production process under supercritical conditions previously described 29,30 . The diameter of the NPs is 3.6 nm for TiO 2 and 5 nm for ZrO 2 (standard deviation 1 nm).…”

Hydrothermal growth of ZnO nanostructures in supercritical domain: Effect of the metal salt concentration (Zn(NO3)2) in alkali medium (KOH)

“….) [24,25]. The morphology and the size can be tuned by changing experimental conditions such as temperature, pressure, reaction time, pH, nature and concentration of the metallic precursor and the alkali solution.…”