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Superelastic oxide micropillars enabled by surface tension–modulated 90° domain switching with excellent fatigue resistance

Significance We demonstrate the micropillars of normally brittle BaTiO3 (BTO) are superelastic as well as fatigue resistant over 1 million cycles without accumulating residual strains or noticeable variation in stress–strain curves over cycles. The mechanism of reversible 90° domain switching identified in our work is advantageous over the conventional phase transition mechanism as found in ZrO2 and shape memory alloys, and it is not limited to BTO. Therefore, our work offers a promising strategy for realizing fatigue-resistant superelasticity in otherwise brittle ferroelectric materials. Superelastic materials capable of recovering large nonlinear strains are ideal for a variety of applications in morphing structures, reconfigurable systems, and robots. However, making oxide materials superelastic has been a long-standing challenge due to their intrinsic brittleness. Here, we fabricate ferroelectric BaTiO3 (BTO) micropillars that not only are superelastic but also possess excellent fatigue resistance, lasting over 1 million cycles without accumulating residual strains or noticeable variation in stress–strain curves. Phase field simulations reveal that the large recoverable strains of BTO micropillars arise from surface tension–modulated 90° domain switching and thus are size dependent, while the small energy barrier and ultralow energy dissipation are responsible for their unprecedented cyclic stability among superelastic materials. This work demonstrates a general strategy to realize superelastic and fatigue-resistant domain switching in ferroelectric oxides for many potential applications.