Large non-linear piezoelectric effect due to recoverable domain switching

Linear piezoelectricity is known to be caused by the coupling of polarization to the lattice deformation, so that an external stress can cause a small change in polarization through lattice deformation. Such an effect is linear but weak in principle. In many cases piezoelectric materials may endure high stresses, which can cause partial domain switching. Such domain switching can contribute in a significant way to an enhanced piezoelectric effect. However, the enhancement is meaningful only when the domain switching is reversible; otherwise the piezoelectric effect would suffer degradation during cycling. In theory it seems unlikely to achieve a reversible domain switching because different domain states are energetically identical and there is no inherent driving force for a reversible domain switching. In the present study, we report a large non-linear piezoelectric effect due to a reversible domain switching in an aged acceptor-containing BaTiO₃ ceramic. Compared with the linear piezoelectricity of d₃₃ ∼ 100pC/N, the non-linear piezoelectricity showed an equivalent d₃₃ of 200pC/N at high stress. We suggest that this non-linear effect originates from the reversible non-180^o domain switching, driven by a symmetry conforming tendency of point defects (oxygen vacancies). Our work may provide new insight into the understanding and utilization of the enhanced piezoelectricity at high stress.