Piezoelectricity and local structural distortions in (Na0.5Bi0.5)1-xSrxTiO3-Bi12TiO20 flexoelectric-type polar ceramics

摘要

We have previously described sintered Na0.5Bi0.5TiO3-Bi12TiO20 composites as flexoelectric-type polar ceramics because they have a net macroscopic flexoelectric polarization. Here, we report on the universal existence of the macroscopic flexoelectric polarization in the (Na0.5Bi0.5)1-xSrxTiO3-Bi12TiO20 system, in which enhanced piezoelectricity is observed. By combining Raman spectroscopy and x-ray photoelectron spectroscopy techniques, we have identified the local flexoelectric polarization as distorted BiO5 polyhedra and TiO6 octahedra in the SrTiO3-Bi12TiO20 ceramic. The macroscopic polarization may be due to the partial alignment of these distorted units located within the grain boundary amorphous phases. Bi12TiO20 could have an important role in these flexoelectric-type polar ceramics.