Exploring the role of charge–lattice coupling in the structural phase transition in BaCeO3

Abstract

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.