Phonon Dynamics and Inelastic Neutron Scattering of Sodium Niobate

Abstract

Sodium niobate (NaNbO3) exhibits most complex sequence of structural phase transitions in perovskite family and therefore provides as excellent model system for understanding the mechanism of structural phase transitions. We report temperature dependence of inelastic neutron scattering measurements of phonon densities of states in sodium niobate. The measurements are carried out in various crystallographic phases of this material at various temperatures from 300 K to 1048 K. The phonon spectra exhibit peaks centered around 19, 37, 51, 70 and 105 meV. Interestingly, the peak around 70 meV shifts significantly towards lower energy with increasing temperature, while the other peaks do not exhibit an appreciable change. The phonon spectra at 783 K show prominent change and become more diffusive as compared to those at 303 K. In order to better analyze these features, we have performed first principles lattice dynamics calculations based on the density functional theory. The computed phonon density of states is found to be in good agreement with the experimental data. Based on our calculation we are able to assign the characteristic Raman modes in the antiferroelectric phase to the A1g symmetry, which are due to the folding of the T (w=95 cm-1) and delta(w=129 cm-1) points of the cubic Brillouin zone.

arXiv comment19 pages, 8 figures, 2 tables

References in corpus (6)

• First-principles study of epitaxial strain in perovskites
• Competing antiferroelectric and ferroelectric interactions in NaNbO3 : Neutron diffraction and theoretical studies
• Phase stability and structural temperature dependence in sodium niobate: A high resolution powder neutron diffraction study
• Origin of the large phonon band-gap in SrTiO3 and the vibrational signatures of ferroelectricity in ATiO3 perovskite: First principles lattice dynamics and inelastic neutron scattering of PbTiO3, BaTiO3 and SrTiO3
• Suppression of Antiferroelectric State in NaNbO3 at High Pressure from In Situ Neutron Diffraction
• Relative phase stability and lattice dynamics of NaNbO${}_3$ from first-principles calculations

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• High Temperature Phase Stability in Li0.12Na0.88NbO3: A Combined powder X-Ray and Neutron Diffraction Study
• Evidence for existence of Functional Monoclinic Phase in Sodium Niobate based Solid Solution by Powder Neutron Diffraction