Fatigue of lead zirconate titanate ceramics.: I:: Unipolar and DC loading

In actuator applications, a degradation of the ferroelectric material occurs both under unipolar cycling as well as DC loads. The developing material state is characterized by measurements of large and small signal unipolar as well as bipolar hysteresis loops. While the unipolar loops indicate a small decrease in strain and polarization amplitudes, the bipolar loops unveil the development of an offset field, an offset polarization, and an asymmetry in the hysteresis of strain and dielectric constant. A mechanism for unipolar fatigue is suggested to explain the observed changes in material properties with cyclic loading.