Acoustic emission from different PZT

Acoustic Emissions (AE) in ferroelectrics originate from three major source s: domain pattern changes, electric discharges and microcracking. All three may play a significant roll as damage mechanisms for the long term reliabi lity of these materials in actuator applications. In this publication, cont ributions of at least two mechanisms in commercial PZT's are presented and the feasibility of a unique assignment of emission signature to mechanism i s discussed. Soft PZT's show a distinct threshold for the first appearance of AE during poling. Large strain changes in these materials due to "easy" domain wall motion do not yield AE while high strain levels generate cascad ed events. Subsequent polarization reversals generate AE events at lower fi elds. Hard PZT's continuously generate AE during the whole hysteretic cycle with no observable field levels of "easy" deformation. Domain wall motion is contrasted to the energy release of elastically prestressed domain state s, domain nucleation, discharges and microcracking.