A number of experiments have proved that polarization clusters exists in BaTiO3 and excellent properties of BaTiO3 are related to a great extent with spatiotemporal information of polarzition clusters. The measurement of temporal state is essential to discuss the characteristics of the polarization clusters and to recognize the nature of the ferroelectric phase transition. In our experiment

the 300 nm long range polarization clusters in BaTiO3 were found to be dynamic with characteristic relaxation time (τc) of several microseconds by Photon Correlation Spectroscopy (PCS). The evolution details of the relaxation time were also revealed clearly in the vicinity of TC. It has proved that PCS is an effective method for the probing of dynamic process among ferroelectrics.