Facilitated reversible domain switching at multiphase boundary in periodically orthogonal poled KNN-based ceramics: Strain versus non-180^o 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(o) 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(o) 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 degrees domain, indicating that a large amount of non-180 degrees 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(o) domain switching in the multiphase boundary during periodic orthogonal poling, which can serve as a guide for the design of high-performance KNN materials.