Phonon behaviors and dielectric functions in Bi0.5Na0.5TiO3-based ceramics by Raman scattering and optical ellipsometry |
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| Authors: | Shan Jiao Fangfang Chen Yi Zhang Zhigao Hu Zhihua Duan Feifei Wang Dazhi Sun |
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| Affiliation: | 1. Key Laboratory of Optoelectronic Material and Device, Department of Physics, Shanghai Normal University, Shanghai, China;2. Key Laboratory of Polar Materials and Devices (MOE), Technical Center for Multifunctional Magneto-Optical Spectroscopy (Shanghai), Department of Electronic Engineering, East China Normal University, Shanghai, China;3. Key Laboratory of Resource Chemistry of Education Ministry, Department of Chemistry, Shanghai Normal University, Shanghai, China |
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| Abstract: | The dielectric functions and lattice vibrations of (0.935-x)Bi0.5Na0.5TiO3-0.065BaTiO3-xSrTiO3 (BNBSTx) ceramics were investigated by temperature-dependent 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 SrTiO3. 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 TiO6 tilting and the off-center displacement of Ti4+. These results seem to be significant for the enhanced response functions with the addition of SrTiO3 in BNBSTx ceramics. |
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