Effects of residual stress caused by abrasion on the flexoelectric response of BaTiO₃ ceramics

The spontaneously polarized surface layer, which originates from stress relaxation, has been proposed for the unexpectedly large flexoelectric response measured in ferroelectric ceramics. However, the source of the stress that led to the polarized surface layer is still not completely known. In this work, the effect of surface stress on the microstructure, dielectric properties and flexoelectric response of BaTiO₃ ceramics abraded by abrasive papers of various grit sizes was systematically studied. Compared with the as-prepared sample, the flexoelectric coefficients of abraded BaTiO₃ ceramics decreased from ~600 μC/m to less than 200 μC/m. The flexoelectric coefficients of all the samples, however, recovered to ~500 μC/m following heat treatment at 200 °C and a subsequent slow cooling process. The results indicate that abrasion can introduce stress on the surface layers and affect the flexoelectric response of ferroelectric ceramics to some extent, but the stress is not the main reason for the formation of polarized surface layers.