Large flexoelectric-like response of SrTiO3 ceramics sintered in the reducing atmosphere

The relatively low flexoelectric coefficient of SrTiO3 (STO) ceramics severely restricts their effectiveness in practical applications. Treatment under reducing conditions or low oxygen pressure is an effective way to increase their flexoelectric coefficients. In this work, STO ceramics with a large flexoelectric coefficient (reaching 1300 μC/m) were prepared by sintering under N2/H2 reducing atmosphere. We demonstrated that there is inhomogeneity of oxygen vacancies in the surface layer of the reduced ceramics. The surface layer may be transformed into a ferroelectric phase and polarized due to the existence of inhomogeneously distributed oxygen vacancies. These research findings provide an in-depth understanding of the mechanism of the flexoelectric response and a feasible strategy to improve the response of STO ceramics.