Analysis of high temperature reduction process of Na0.5Bi0.5TiO3-based ceramics

Lead-free metamaterials with enormous effective apparent piezoelectric response has been fabricated by applying an asymmetric chemical reduction to Na0.5Bi0.5TiO3 (NBT)-based ceramics. To achieve high performance, optimization of the reduction conditions is required. In this study, we analyzed the effect of reduction temperature and time on the reduction thickness of NBT-based ceramics. We found that the reduction reaction between NBT-based ceramics and graphite is an interface reaction rate-controlled process. The reduction thickness has a linear relationship with the reaction time at a fixed reduction temperature. The lower activation energy of NBT-based ceramics than that of lead-based materials indicates the lead-free ceramics are easier to be reduced. The effect of the reduction on the flexoelectric-like response was further explored, and the maximum response ( >1 mC/m) was measured in the ceramics having a reduction-thickness-to-total-thickness ratio of around 0.28. This study provides a guideline to optimize the fabrication conditions of the NBT-based metamaterials.