Raman and infrared spectroscopic investigations on the crystal structure and phonon modes of LaYbO3 ceramics

LaYbO3 is a highly distorted perovskite with orthorhombic structure. However, its exact space group has been a matter of debate. Both the polar Pna2(1) and the centrosymmetric Pnma space groups, with Z = 4, have been proposed to describe its structure at room temperature. In this work we present optical spectroscopic investigations by Raman scattering and infrared reflectivity of LaYbO3 ceramics sintered at 1600 degrees C. The results allowed us to propose a new centrosymmetric Cmcm space group for this compound, and to show which phonons give the main contributions to its dielectric constant and quality factor at microwave frequencies.