Normal-incommensurate phase transition in (Sr1−xBax)2Nb2O7 ferroelectric single crystals

Micro-Brillouin and Raman light scattering experiments were performed on (Sr1−xBax)2Nb2O7 single crystals to investigate the effect of Ba addition on the normal-incommensurate phase transition. From the Brillouin frequency shift results, it was observed that the onset temperature of the normal-incommensurate phase decreased with increasing Ba concentration. This was associated to the suppression of the octahedra tilting due to substitution of larger ion on the A-site. The Raman intensity of the Q soft mode measured at room temperature also showed a similar behaviour with increasing x.