Effect of Ca Content on the Acoustic Anomalies of Ba1-xCaxTiO3 Single Crystals Studied by Brillouin Light Scattering

Abstract

The acoustic anomalies of the longitudinal acoustic mode of Ba1-xCaxTiO3 single crystals with x = 0, 0.12, and 0.20 were investigated in a wide temperature range of 290 similar to 873 K by using a Brillouin light scattering technique. The remarkable changes in the Brillouin frequency shift and the half width of this acoustic mode were attributed to the coupling between the acoustic mode and the polarization fluctuations induced by the precursor polar clusters near the ferroelectric phase transition temperature. The relaxation time estimated from the acoustic mode anomaly showed a critical slowing down behavior and increased with the Ca content. This indicates that the addition of Ca ions at A sites of the perovskite structure of BaTiO3 induces an additional polarization component due to its off-center displacements, thus making the cluster dynamics more sluggish than it is in pure BaTiO3.