Temperature dependent phase transition of (Bi0.5Na0.5)1−xBaxTiO3 lead-free piezoelectric

Abstract Phase transformation and electric properties of lead-free piezoceramics (Bi 0.5 Na 0.5 ) 1− x Ba x TiO 3 with x =0.05, 0.06, and 0.07(BNB5T, BNB6T and BNB7T) were investigated using dielectric, piezoelectric and ferroelectric measurements. Electric field induced strain measurement shows “W” shape bipolar strain characteristics for BNB5T with typical ferroelectric P – E curve, while BNB6T and BNB7T, possessing pinch-off P – E , exhibit “V” shape field-induced strain. All the BNB x T specimens exhibit relaxor characteristic, identified by the Debye Law. Dielectric properties measured at elevated temperatures with the frequency variation (10–500 kHz) reveal frequency dispersion below the T d point, but no dispersion between T d and T m , which may be ascribed to an intermediate phase transition. By adding more Ba 2+ ions, the region of intermediate phase, distinguished by frequency dependence dielectric constant, expands to lower temperature. Moreover, the ferroelectric properties measured at elevated temperature were carried out below and at the depolarization temperature to well investigate the existence of this phase. Much less e – T profile dispersion were observed during the investigation of BNB6T and BNB7T, leading to possible existence of an intermediate phase in the investigated compositions. The results suggest that the linear field-induced-strain of (Bi 0.5 Na 0.5 ) 1− x Ba x TiO 3 are expected to be attributed to the intermediate phase.