Partially transformed relaxor ferroelectric single crystals with distributed phase transformation behavior

摘要

Relaxor ferroelectric single crystals such as PMN-PT and PIN-PMN-PT undergo field driven phase transformations when electrically or mechanically loaded in crystallographic directions that provide a positive driving force for the transformation. The observed behavior in certain compositions is a phase transformation distributed over a range of fields without a distinct forward or reverse coercive field. This work focuses on the material behavior that is observed when the crystals are loaded sufficiently to drive a partial transformation and then unloaded, as might occur when driving a transducer to achieve high power levels. Distributed transformations have been modeled using a normal distribution of transformation thresholds. A set of experiments was conducted to characterize the hysteresis loops that occur with the partial transformations. In this work the normal distribution model is extended to include the partial transformations that occur when the field is reversed before the transformation is complete. The resulting hysteresis loops produced by the model are in good agreement with the experimental results.