Mechanisms of aging and fatigue in ferroelectrics

A comprehensive review of aging and fatigue phenomena in bulk polycrystalline ferroelectrics is presented. Three material classes are covered, namely the most widely used Pb[Zr1−xTix]O3 (PZT) ceramics and lead-free materials, including those based on bismuth sodium titanate Bi1/2Na1/2TiO3 (BNT) and alkali niobate [KxNa1−x]NbO3 (KNN). Aging is studied in poled and unpoled states both experimentally and theoretically. The variety of different loading regimes for fatigue includes DC electric field, unipolar, sesquipolar and bipolar cycling and all these differently combined with mechanical loading at different frequencies and temperatures. The role of device geometries and electrode materials is addressed and models describing charge migration and defect dipole re-orientation are discussed in the context of recent experimental studies.