Doping effect on the phase transition temperature in ferroelectric SrBi _(2-x)Nd _xNb _2O _9 layer-structured ceramics: A micro-Raman scattering study

摘要

The temperature dependence of Raman spectra for SrBi _(2-x)Nd _xNb _2O _9 ceramics (x from 0 to 0.2) has been studied in a wide temperature range from 80 to 873 K. It is found that the peak position of the A _(1g)[Nb] phonon mode at 207 cm ~(-1), which is directly associated with the distortion of NbO _6 octahedron, decreases with increasing Nd composition, while the A _(1g)[O] phonon mode at 835 cm ~(-1) increases. Moreover, both the peak position and intensity of the A _(1g)[Nb] phonon mode reveal strong anomalies around the ferroelectric to paraelectric phase transition temperature. It indicates that the phase transition temperature decreases from about 710 to 550 K with increasing Nd composition, which is due to the fact that the introduction of Nd ions in the Bi _2O _2 layers reduces the distortion extent of NbO _6 octahedron.