Bi1/2Na1/2TiO3-based ceramics are a group of promising lead-free piezoelectric materials that are being studied more and more intensely at present. Large displacement actuation is one of the important applications of piezoelectric materials. Because the piezoelectric constant of BNT-based ceramics measured by the Berlincourt method is no more than 150pC/N, it seems that the materials are not suitable for large displacement actuation. However, in our work it was found that BNT-BT ceramic wafers could produce very large displacement under DC electric field, although the piezoelectric constant measured by Berlincourt method was very small. It makes them possible to be used as large displacement actuator. There are two possible mechanisms for this phenomenon. The first mechanism may be related to the semiconductivity of BNT-BT ceramics. In this case, the BNTBT ceramic wafers are similar to a monomorph device. The other possible mechanism may be associated with the anomalously intense space charge effect in the materials.

Keywords: Bi1/2Na1/2TiO3, Lead-free, Piezoelectric ceramics, Large displacement, Monomorph, Space charge