ABSTRACT
INTRODUCTION Ferroelectric (FE) fatigue is well known to be the loss of switchable polarization by
repeated polarization reversals. Over the last decades several fatigue mechanisms have been proposed which invoke (a) electronic charge trapping at domain walls [1-4], (b) doubly positively charged ionic defect sites such as oxygen vacancies (V0**) pinning domain walls [5-8], (c) poling charged defect-dipoles; these dipoles are believed to become aligned during cycling and are very slow to reverse, thus, reducing or canceling some of the switched lattice polarization [9], (d) decreasing electrode adhesion, as well as (e) microcracking [1], to name a few. It is impossible to distinguish between these possible degradation processes from purely electrical measurements, however, significant insight has been provided through studies of different electrode materials [5,10-13] and photoinduced fatigue and restoration [3,4,14].
