Dual superelasticity: A pathway to exceptional and modulable deformation

Inorganic ferroelectric materials often suffer from brittleness. Superelasticity is a notable stress-strain behavior characterized by the recovery of large amount of nonlinear “plastic” strains. This offers a promising approach to overcome the deformation limitation of inorganic ferroelectric materials, enabling their applications in sensors, actuators and dampers. However, precise modulation of superelasticity remains elusive, and further improvement of superelastic deformation is still essential. This paper reveals, for the first time, the critical role of shear elastic energy density as the fundamental mechanism governing superelasticity in these materials. Leveraging this insight, we predict and demonstrate a dual superelasticity behavior with excellent deformation ability, which is not realized in single-crystal ferroelectrics. This dual superelasticity behavior stems from the significant and sustained presence of shear elastic energy density. The diagram for superelastic behavior under the modulation of multi-fields reveals the existence of five distinct superelasticity states in single-crystal ferroelectrics. Crucially, the dual superelasticity delivers a remarkable 30.5 % improvement in total recoverable strain compared to a traditional none superelastic stress-strain curve, and a 17 % gain over a single superelasticity, representing a breakthrough in achievable deformation. The multi-levels superelastic behavior and the corresponding shear elastic energy density centered mechanism offer a solution specifically designed to address the brittleness drawback of inorganic ferroelectric devices especially under complex multi-fields environments.