A low frequency Raman study of SrBi2Ta2O9-Bi3TiNbO9

Raman spectra of SrBi2Ta2O9 (SBT), Bi3TiNbO9(BTN), and x(SBT) + (1-x)(BTN) samples were studied for the first time in the low frequency region. The BTN spectra show two features around 33 and 41 cm(-1), while only one feature, around 30 cm(-1), is found in SET. The stoichiometric evolution of the Raman spectra shows that the frequency positions of these bands decrease as x changes from 0 to 1. Strong correlation is found between the frequency positions of these modes and both the Curie temperature and the a-parameter. The results are interpreted in terms of the ferroelectric displacive modes, which are responsible for the strong spontaneous polarization along a-axis. The band around 65 cm(-1) is assigned to oxygen motion in the B2O2 layer.