Extraordinarily Large Contribution Ratio of Ferroelastic Domain Switching to Piezoresponse in Monoclinic (K, Na)NbO₃ Films

Abstract

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 (K0.4Na0.6)NbO3 (KNN) film epitaxially grown in monoclinic phase on Nb‐doped SrTiO3, 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.

Novel Route for Enhancing Piezoelectricity of Ferroelectric Films: Controlling Nontrivial Polarization States in Pb(Zr, Ti)O3 Monodomain Superlattice Structure

“…To deal with this issue, more efforts have been devoted to manipulating the non-180° motions of ferroelectric domain walls. − This strategy was first inspired by the discovery of the morphotropic phase boundary in Pb­(Zr, Ti)­O 3 (PZT) and gradually acknowledged by researchers as the extrinsic effect. , In recent years, approaches to utilizing the extrinsic effect have been further developed. For example, strain engineering has been proved to be effective in controlling the domain structure via adjusting mechanical energy in the film. − Fabrication of multilayer or superlattice films has been reported where ferroelectric domains can be refined within one layer in such structures, and the domain walls are easy to move with an external electric field. − …”