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Abstract
Acoustic Emissions (AE) in ferroelectrics originate from three major sources: domain pattern changes, electric discharges and microcracking. All three may play a significant roll as damage mechanisms for the long term reliability of these materials in actuator applications. In this publication, contributions of at least two mechanisms in commercial PZT's are presented and the feasibility of a unique assignment of emission signature to mechanism is 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 cascaded events. Subsequent polarization reversals generate AE events at lower fields. 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 states, domain nucleation, discharges and microcracking.
