Large Electric Field-Induced Strain and Antiferroelectric Behavior in (1-x)(Na0.5Bi0.5)TiO3-xBaTiO3 Ceramics

The dielectric, ferroelectric, and electric field-induced strain response of (1-x)(Na0.5Bi0.5)TiO3-xBaTiO3 (NBT-BT) (0.04 ≤ x ≤ 0.10) ceramics has been systematically investigated as a function of temperature. It is found that ferroelectric and antiferroelectric (AFE)-like behavior can coexist at temperatures significantly lower than the depolarization temperature Td (even down to as low as ambient temperature). Electron microscopy suggests that such behavior results from the electric field-dependence of fine scale octahedral tilt twinning disorder and the associated disorder in the local (ferroic) off-center displacements of the Na/Bi/Ba and Ti ions. The existence of the AFE-like behavior significantly enhances the electric field-induced strain. High bipolar strain of 0.40% and unipolar strain of 0.27% has thereby been achieved at ambient temperature in an NBT-BT, x = 0.07, ceramic. The bipolar and unipolar strains reach almost identical maximum values when the temperature is close to Td. Giant unipolar strains of 0.42%, 0.41%, and 0.29% were observed in NBT-BT ceramics with x = 0.06, 0.07, and 0.08 at temperatures close to their Td’s of 100 °C, 50 °C, and 87 °C, respectively. This work thus provides new insight into ways to further optimize lead-free NBT-BT piezoelectric ceramics for practical use in different temperature ranges.