Lattice dynamics and Raman spectrum of supertetragonal PbVO3. (February 2023)

• Record Type: Journal Article
• Authors: Bouvier, Pierre; Sasani, Alireza; Bousquet, Eric; Guennou, Mael; Moreira, Joaquim Agostinho
• Is Part Of: Journal of physics and chemistry of solids. Volume 173(2023)
• Publication Date: 2023-02
• Subjects: lead vanadate -- Supertetragonal perovskite -- Polarized Raman spectroscopy -- DFT simulations -- Lattice dynamics; Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2022.111092
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: Lead vanadate PbVO3 is a polar crystal with a P 4 mm space group under ambient conditions. PbVO3 is isostructural with the model soft mode-driven ferroelectric PbTiO3, but it differs due to the so-called "supertetragonal" elongation of its unit cell. In this study, we investigated the lattice dynamics of PbVO3 based on Raman spectroscopy at room temperature and first-principle calculations. All zone-center transverse optical phonon modes were identified by polarized, angle-dependent Raman spectroscopy and assigned as follows: E modes at 136, 269, 374, and 508 cm −1 ; A1 modes at 188, 429, and 874 cm −1, and B1 mode at 319 cm −1 . The calculations confirmed the experimental symmetry assignment and allowed us to obtain the longitudinal optical phonon wavenumbers. In addition, we analyzed the mode eigenvectors in detail in order to identify the atomic displacements associated with each mode and compare them with PbTiO3 . Despite differences in chemistry and strain, the phonon eigenvectors were found to be highly comparable in both compounds. We investigated the position of the ferroelectric soft mode in PbVO3 compared with PbTiO3 . Sizeable splitting of the B1 +E modes appeared as a characteristic feature of supertetragonal phases. The peculiarity of the vanadyl V–O bond frequency in PbVO3 was also addressed. Highlights: The symmetry, wavenumber position and tensors components of all the transversal Raman active optical phonons are presented for supertetragonal PbVO3 . A large splitting of the E-B1 modes is found as a characteristic feature of supertetragonal phases. A scaled comparison using the c/a ratio between the PbVO3 and PbTiO3 phonons is presented, based on the DFT calculations results. The VO stretching A1 Raman mode at 874 cm -1 is identified as a polar mode and displays a large anisotropy in its Raman tensor values.