Tomoaki Yamada

Ferroelectric monoclinic phases have attracted exceptional attention as the origin of giant piezoelectricity, whilst the detailed contributions of ferroelastic domain switching and electric‐field induced lattice strain to the piezoelectric response remain still challenging to clarify. In this work, these contributions to the piezoelectric response are deconvoluted in a (K 0.4 Na 0.6 )NbO 3 (KNN) film epitaxially grown in monoclinic phase on Nb‐doped SrTiO 3 , where the as‐deposited film feature (111) and () non‐180° domains. By time‐resolved synchrotron X‐ray diffraction, the ferroelastic domain switching and electric‐field induced lattice strain subjected to an ultrafast electric‐field pulse are quantitatively probed. The switching of ≈4% volume fraction of (111) domains into () ones by a moderate electric field and its response within 30 µs as well are unambiguously unveiled. Interestingly, the contribution of domain switching to the strain is larger than the total strain of the film, which is enabled because of the negative electric‐field‐induced lattice strain. The present study connects macroscopic piezoelectric response in KNN films with the underlying microscopic origins unveiled by separating two contributions, which may provide a knowledge platform that allows for significant achievement of practical lead‐free piezoelectric microelectromechanical and nanoelectromechanical systems in the future.