Domain Switching by Applied Electric Field in (001) and (111)-epitaxial (K0.5Na0.5)NbO3Films

(K
_1-x
Na
_x
)NbO
₃
(KNN) is especially paid attention to as a lead-free piezoelectric material. It is known that KNN has a morphotropic phase boundary (MPB) at x ~ 0.5, which shows a high piezoelectric property. However, it has not been fully clarified how the domain structure of KNN changes by applied electric field. In this study, we observed electric field-induced strain and domain fraction change of KNN films by synchrotron X-ray diffraction.