Supplement Number 1

Dielectric permittivity and dielectric loss were measured as a function of temperature on poled ceramic samples. As shown in Fig. S1(a) and (b), no dielectric anomalies could be found in the temperature range of 25-150 {degree sign}C for these two samples. The thermogravimetric analysis (TGA) were also performed. No clear peak could be observed in the TGA results as shown in Fig. S1(c) and (d). Therefore, no macroscopic phase transition esist in the ceramcis around 50 {degree sign}C