Electrical fatigue in 0.94Na0.5Bi0.5TiO3–0.06BaTiO3: Influence of the surface layer

Abstract

Similar to several Pb-based relaxor ferroelectrics, 0.94Na0.5Bi0.5TiO3–0.06BaTiO3 is reported to have a micrometer-sized surface layer. We hypothesize that since this layer has structural properties distinct from the bulk, it would undergo a different property degradation than the bulk during cyclic electrical loading or fatigue. First, we show the existence of a surface layer by comparing X-ray diffraction patterns of the ceramic surface and powders. Then, we show that fatigue damage is mainly localized in the surface layers, and thus, property degradation due to fatigue can be recovered on removing the affected surface layer. We also show that ion migration may be occurring in the surface layer during fatigue experiments using secondary ion mass spectroscopy, where the ion sources may be the sample itself, the electrode layer or the insulating oil in which the experiment is performed. Finally, we show that permanent fatigue damage such as microcracks is dependent on the choice of electrodes. While permanent damage was observed for Pt electrodes, it was not present for oxide electrodes, suggesting that oxygen permeation and accumulation at the electrode/surface interface may play a role in the formation of observed microcracks. In summary, we have shown that fatigue is influenced by the surface layer, and surface layer damage can be controlled using the selection of electrodes.