Abstract
Sodium trititanate Na2Ti3O7 microcrystals were carefully prepared by
sodium carbonate and titanium dioxide solid-state reaction and
characterized by scanning and transmission electron microscopies,
selected area electron diffraction, X-ray powder diffraction, and Raman
and Fourier transform infrared spectroscopies. Electron microscopic
techniques revealed that the samples were formed by elongated particles
several microns long with broad size distributions. The zone axis and
crystal growth direction of the elongated particles were determined by
selected area electron diffraction. These results were useful for
identifying the symmetries of the optical vibrational modes obtained by
infrared absorption and polarized Raman scattering of oriented crystals.
For a complete assignment of the depicted phonon modes, Fourier
transform infrared spectroscopy and Raman data were compared with
theoretical data obtained from first-principles calculations within the
framework of the density functional theory. A very nice agreement was
established between the characteristic features of measured and
calculated vibrational modes. In particular, all optical phonon modes of
Na2Ti3O7 could be experimentally observed and assigned to their correct
symmetries. These results must be useful for describing the physical
behavior of the system and designing new technological applications.
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