Brillouin spectroscopic study of central peak in NaNbO3 single crystal

Anti-ferroelectric NaNbO3 single crystals were grown by flux method. Brillouin spectroscopy was used for the first time to investigate the central peak in both P and R phases and across P–R phase transition temperature TC at 643 K. The temperature dependence of relaxation time and that of integrated intensities of central peak (CP) are found to show anomalies across TC. The relaxation time of CP shows a critical slowing down in the vicinity of phase transition implying the nature of the transition to be order–disorder type. An activation energy for the Nb-ion movement between two equivalent sites is estimated to be 105 ± 10 meV. In addition, a comparison of the temperature evolution of integrated intensities of CP and low frequency modes suggest that these are uncoupled.

► Brillouin scattering is used in NaNbO3 single crystal. ► The polarization fluctuation relaxation through the central peak is probed across P-R phase transition. ► The nature of the P-R phase transition is shown to be order-disorder type. ► The relaxation rate is found to exhibit a critical slowing down behavior near TC. ► An activation energy for Nb-ion hopping between occupied and vacant sites is estimated.