Vibrational analysis on two-layer Aurivillius phase Sr1−xBaxBi2Nb2O9 using Raman spectroscopy

A Raman spectroscopy study at room temperature was carried out on Sr1−xBaxBi2Nb2O9 ferroelectric ceramics (x = 0, 15, 30, 50, 70, 85, 100 at%). The results were compared to the Raman activity of SrBi2Nb2O9(SBN) and has suggested that the Sr2+/Bi3+/Ba2+ mixing at the A sites of the pseudo-perovskite structure leads to a wavenumber shift with the increasing of the barium content in the structure connected to OAO bending mode, which was observed at 222 cm−1, and the OBO bending A1g mode (B = Nb5+), which was observed at 171 cm−1 due to the modification environment by the barium substitution. A wavenumber shift was observed for the NbO stretching A1g mode connected to the NbO6 octahedral, which was observed at 843 cm−1 in the SBN sample, due to the octahedral distortions. The B2g mode was related to the atoms vibration in the (x, y)-plane and was observed at 568 cm−1. This mode was less affected by the barium substitution, which has been attributed to changes in the fluoride layer of the Aurivillius structure. The modes activities were observed to be quite different for x ≤ 30 at% and x ≥ 50 at%, which has been attributed to a higher concentration of Ba2+ into the A sites for the higher barium contents.