Dielectric relaxation modes in bismuth-dopedSrTiO3: The relaxor behavior

The ferroelectric relaxor behavior in Bi-doped ${\mathrm{SrTiO}}_3$ was studied in the temperature range 1.5–300 K and up to 400 MHz. Some interesting results are shown: (1) Typical ferroelectric relaxor behavior develops out of the other impurity relaxation modes. The ferroelectric relaxor peaks occur on the quantum-paraelectric background. The polarization irreversibility effect observed after field cooling or zero-field cooling, and the data of remanent polarization $P_r,$ show that the ferroelectric relaxor behavior is a nonequilibrium phenomenon. (2) The coexistence of the ferroelectric relaxor peak with other impurity modes indicates that there are several kinds of polar clusters which are responsible for different dielectric anomalies in different temperature ranges. This confirms a multicluster state characteristic in ferroelectric relaxors. (3) Near 400 MHz, an additional relaxation process appears, which indicates the possible existence of two polarization processes in a ferroelectric relaxor.