Ferroelectric switching in the Aurivillius phase oxide SrBi₂Ta₂O₉ from first principles

The Aurivillius phases are a family of layered perovskites with general formula Bi_2mA_n−m B_nO_3(n+m) , in which Bi₂O₂layers alternate with perovskite-like blocks. Theoretical and first-principles studies during the past decade have revealed that the coupling of the polarization with non-polar lattice distortions such as octahedral rotations plays a significant role in the structural phase transitions and ground state ferroelectric structure of the Aurivillius phase oxide SrBi₂Ta₂O₉. However, the implication of this coupling on the ferroelectric switching mechanism, which requires that one of the octahedral rotations must reverse along with the polarization, has received minimal attention. Here, we use density functional theory calculations and group theoretic analysis to explore symmetry-distinct intrinsic ferroelectric switching pathways of SrBi₂Ta₂O₉. By tracking the evolution of the non-polar lattice distortions as well as the polarization along each switching path, we uncover how the couplings between multiple lattice distortions facilitate the switching process. This work provides new understanding of the role of non-linear lattice couplings in the ferroelectric switching mechanisms of the structurally complex family of Aurivillius phase oxides.