Piezoelectric thin-film super-lattices without using piezoelectric materials

TL;DR

This paper demonstrates that non-piezoelectric materials can form thin-film super-lattices exhibiting apparent piezoelectricity through odd-layer stacking and flexoelectric effects, enabling high piezoelectric responses.

Contribution

It introduces a method to create effective piezoelectric super-lattices from non-piezoelectric materials using flexoelectricity and odd-layer stacking sequences, with analytical modeling.

Findings

Achievable apparent piezoelectricity can reach 75% of ferroelectric Barium Titanate.

Analytical expressions for super-lattice responses are provided.

Flexoelectricity enables piezoelectric-like behavior in non-piezoelectric multilayers.

Abstract

Abstract: In this paper we show that experimentally realizable apparently piezoelectric thin-film super-lattices can be created from non-piezoelectric materials provided an odd-order (e.g. trilayer) stacking sequence is used. The size-dependent mechanism of flexoelectricity, which couples gradients of strain to polarization, allows such a possibility. We present closed-form analytical expressions for the response of various thin-film and super-lattice configurations. We also clarify some of the subtleties that arise in considering interface boundary conditions in the theory of flexoelectricity as well as the relationship of flexoelectricity to the frequently used polarization gradient terms used in modeling ferroelectrics. We find that for certain (optimum) material combinations and length scales, thin film superlattices yielding apparent piezoelectricity close to 75 % of ferroelectric Barium Titanate may be achievable.