https://nova.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:47140 0.5Bi_0.5TiO₃–0.06BaTiO₃ 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.]]> Wed 14 Dec 2022 15:20:37 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:39195 0.5Bi_0.5)TiO₃-0.06BaTiO₃ (NBT-6BT) relaxor fer-roelectrics were investigated using the Vickers indentation method and computation of crack tip opening displacement. It was found that an unpoled sample had a fracture toughness of around 1.35 MPa m^1/2. In contrast, an electrically poled sample exhibited anisotropy with a lower fracture toughness perpendicular to the poling direction and a higher value in the parallel direction, as compared to the unpoled sample. Upon cyclic electrical loading (with applied electric field amplitudes between 0.73E_C and 1.4E_C), the indented surface crack was found to propagate. In general, the crack grew rapidly during the initial cycles followed by crack arrest, and the principal driving force for crack growth was proposed to be residual stress around the indentation, as evidenced by the limited field dependence of crack growth. There was also a contribution from the electromechanical strain, which played a role at high cycles (>100 cycles) and high fields (>1.3 E_C). Evidence of a saturation threshold of crack propagation is an advantage for the electromechanical reliability of relaxor ferroelectrics in devices.]]> Thu 26 May 2022 15:54:29 AEST ]]>