Phonon dynamics and inelastic neutron scattering of sodium niobate

Article

关键词: INDUCED PHASE-TRANSITIONS;    RAMAN-SCATTERING;    LEAD-FREE;    SUBMICROCRYSTALLINE;    MICROCRYSTALLINE;    FERROELECTRICITY;    NANBO3;   

DOI  :  10.1103/PhysRevB.89.184303

来源: SCIE

【 摘 要 】

Sodium niobate (NaNbO3) exhibits an extremely complex sequence of structural phase transitions in the perovskite family and therefore provides an 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 to 1048 K. The phonon spectra exhibit peaks centered on 19, 37, 51, 70, and 105 meV. Interestingly, the peak near 70 meV shifts significantly towards lower energy with increasing temperature, while the other peaks do not exhibit any appreciable shift. 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, which are due to the folding of the T (omega = 95 cm(-1)) and Delta (omega = 129 cm(-1)) points of the cubic Brillouin zone, to the A(1g) symmetry.

【 授权许可】

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