Facilitated reversible domain switching at multiphase boundary in periodically orthogonal poled KNN‐based ceramics: Strain versus non‐180o domain

Although many approaches have been implemented to tailor the strain in potassium sodium niobate (KNN)‐based ferroelectrics, they still suffer from poor strain compared to shape memory alloys and giant magnetostrictive materials. Herein, a strategy of periodic orthogonal poling is implemented in KNN‐based ceramics with multiphase boundaries, and the correlation between the amount of non‐180° domain and strain is established, revealing that the mechanisms of interfacial stresses facilitate reversible domain switching during the periodic orthogonal poling. Owing to the self‐generated interfacial stresses between the adjacent regions with different poling directions, an enhanced strain benefits from non‐180° domain switching, which is reversible during periodic orthogonal poling. The enhancement in strain decreases from O‐T to R‐O‐T to the R‐T phase boundary, which corresponds to the different quantity of the non‐180° domain, indicating that a large amount of non‐180° domains can further boost high strain under periodic orthogonal poling. Notably, a slight frequency‐dependent strain was observed across the frequency range of 1‒50 Hz. Therefore, an ideal strain can be further induced by enhancing the amount of reversible non‐180° domain switching in the multiphase boundary during periodic orthogonal poling, which can serve as a guide for the design of high‐performance KNN materials.