Scientists discover how ferroelectric films can be flexible

    Flexible electronics technology is bringing a smart wearable technology revolution, and ferroelectric materials will play an important role in the field of flexible electronics. Ferroelectric material is a kind of functional material with spontaneous polarization and can realize mechanical energy and electrical energy conversion. However, block ferroelectric oxides show certain brittleness and rigidity. How to achieve superelasticity and flexibility in ferroelectric thin films and apply them in flexible electronic devices is an urgent problem to be solved.

    Focusing on this key scientific problem, professor Liu Ming and Professor Ding Xiangdong of Xi 'an Jiaotong University collaborated to conduct in-depth research on the mechanical behavior of the flexibility and elasticity of ferroelectric single crystal thin film materials, and made a great breakthrough.

    Using water-soluble Sr3Al2O6 as the sacrificial layer, they prepared and exfoliated large areas of self-supporting BaTiO3 (BTO) monocrystalline ferroelectric thin films. Through in-situ bending experiments on the films with nanomechanical arms, they found that THE BTO thin films could be folded 180° and the maximum bending strain was up to ~10%.The experiment also found that after the large Angle compression, with the removal of the external force, the shape of BTO film can bounce back, showing superelastic behavior.It is found that the superelasticity of BTO films may result from the reversible inversion of ferroelectric domains a and C under large strain gradient.At the same time, continuous inversion of polarization occurred between a and C ferroelectric domains, which effectively reduced the energy barrier and avoided the possible fracture caused by domain inversion.In addition, in the bending state, the large strain gradient will also induce significant electrical winding effect, realizing the integration of functional devices based on the electrodynamic coupling, thus further enhancing the functionality of related devices based on the flexible single crystal ferroelectric thin film.

    Based on the above results, similar mechanical behaviors can be expected in other ferroelectric bodies, which provides experimental basis for realizing superelasticity in other ferroelectric single crystal thin films.In addition, the flexible ferroelectric thin film with super elasticity is also a good electric field regulating medium. By combining it with the flexible ferroelectric thin film, the substrate binding effect existing in the heterogeneous junction of traditional multi-iron thin film can be avoided and the magnetoelectric coupling effect can be significantly improved, laying a foundation for the future development of new flexible magnetoelectric devices with small electric field adjustable.