Exploring the role of charge–lattice coupling in the structural phase transition in BaCeO 3

The present study correlates the temperature-dependent structural phase transition and charge-lattice coupling in the BaCeO3 (BCO) material using synchrotron X-ray diffraction (SXRD) and Raman spectroscopy measurements over the temperature range of 303-593 K. The SXRD shows that BCO undergoes a structural phase transition from an orthorhombic to a body-centered orthorhombic crystal structure near ∼528 K. A detailed analysis of the structural distortion in terms of Ba-O and Ce-O bond lengths and Ce-O-Ce bond angles has been carried out. The systematic temperature-dependent Raman measurements show significant modifications in phonon dynamics and indicate a signature of a phase transition near ∼533 K. The asymmetry broadening of the Raman modes is explained by the Fano formalism of charge-lattice coupling. Furthermore, to support our findings, the theoretical approach of Helmholtz free energy considering the charge-lattice coupling term has been adopted.