In Situ Polarized Light Microscopy on the Stability of AC Poling During Aging in PMN–28PT Single Crystal

ABSTRACT Materials degradation was investigated on lead magnesium niobate–28% lead titanate (PMN–28PT) single crystal after alternating current poling (ACP) and direct current poling (DCP) conditions as a function of time‐dependent aging and aging from linear electric field cycling. The behavior of the bulk material properties was directly correlated with the ferroelectric domain dynamics determined from birefringence, extinction angle, and transmittance images. These images were acquired during polarized light microscopy using a fully automated process, in combination with dielectric permittivity measurements, to determine domain formation during poling; domain reconfiguration as a function of temperature across different symmetry phases; high temperature time‐dependent aging; and aging from linear electric field cycling. From extinction angle analysis, the monoclinic B (M B )—monoclinic C (M C )—tetragonal (T)—cubic (C) phase sequence was determined for both poling conditions. A diffuse domain configuration with non‐180 domain orientation was obtained from DCP, whereas ACP reveals a large volume fraction difference on the extinction angle areas associated with ferroelectric domains as well as static charge domain walls, which are also responsible for the ACP enhancement. Additionally, it is experimentally demonstrated that the ACP domain configuration is more stable against degradation than the DCP domain configuration due to a reduced non‐180 domain walls found after ACP.