Crystal structure and phononmodes of ilmenite-type NaBiO_3 investigated by Raman and infrared spectroscopies

摘要

NaBiO_3 is an ilmenite-type compound presenting a trigonal structure. In this work, we have performed optical spectroscopic investigations using Raman scattering and infrared reflectivity for this material. By using group-theory calculations, it was possible to determine the number of optically activemodes. Fitting procedures besides Kramers-Kronig (KK) procedures lead to a consistent collection of phonon modes. The Raman spectrum showed nine active first-order modes, while the infrared one revealed eight polar phonons, in good agreement with the theoretical predictions. The results allowed us to confirm the R3- (#148) space group for this compound, and to establish a set of active phonons not yet reported in the literature.