We report the dynamics of soft phonon modes and their role towards the various structural transformations in Aurivillius materials by employing terahertz frequency-domain spectroscopy, atomic pair distribution function analysis, and first-principles calculations. We have chosen Bi4Ti3O12 as a model system and identified soft phonon modes associated with the paraelectric tetragonal to the ferroelectric monoclinic transition. Three soft phonon modes have been discovered which exhibit a strong temperature dependence. We have determined that the anharmonicity in Bi-O bonds plays a significant role in phonon softening and that Bi cations play an important role in the emergence of ferroelectricity.
@article{arxiv.1609.00859,
title = {Soft Phonon Mode Dynamics in Aurivillius Type Structures},
author = {Deepam Maurya and Ali Charkhesht and Sanjeev K. Nayak and Fu-Chang Sun and Deepu George and Abhijit Pramanick and Min-Gyu Kang and Hyun-Cheol Song and Marshall M. Alexander and Djamila Lou and Giti A. Khodaparast and S. Pamir Alpay and N. Q. Vinh and Shashank Priya},
journal= {arXiv preprint arXiv:1609.00859},
year = {2017}
}