Phonon behaviors and dielectric functions in Bi_0.5Na_0.5TiO₃‐based ceramics by Raman scattering and optical ellipsometry

Abstract

The dielectric functions and lattice vibrations of (0.935-x)Bi 0.5 Na 0.5 TiO 3 -0.065BaTiO 3 -xSrTiO 3 (BNBSTx) ceramics were investigated by temperaturedependent spectroscopic ellipsometry and Raman scattering. Based on the analysis of dielectric functions with the Tauc-Lorentz dispersion model, it was found that the band gap and the temperature coefficient increased with the addition of SrTiO 3 . Moreover, the frequency, intensity and/or full width at half maximum of phonon modes related to Bi and Ti-localized phonon modes exhibited local maximum/minimum around the depolarization temperature and permittivity-maximum temperature, which indicated the ongoing structural transformation. In addition, the Sr introduction affected the TiO 6 tilting and the off-center displacement of Ti 4+ . These results seem to be significant for the enhanced response functions with the addition of SrTiO 3 in BNBSTx ceramics.

High‐temperature dielectric and energy storage properties of Bi0.5Na0.5TiO3‐based ceramics modified by Sr0.8Na0.4Nb2O6

“…30,31 Moreover, Raman peaks in the second and third regions slightly move to lower wavenumber with increasing SNN content (Figure 2B). The shift of Roman peaks indicates the decrease of anisotropy in unitcell 32 and the dominant of pseudocubic relaxor phase, 33,34 which is consistent with the XRD results. The SEM surface morphologies of thermal-etched BNT-BT-xSNN ceramics are shown in Figure S1.…”