Society and industry are increasingly calling upon novel materials to enable new capabilities and new applications. One example of a class of materials that is growing in terms of its use and technological impact are ferroelectric materials. These materials can produce a voltage or electric current when subjected to force (i.e., when compressed or bent) or vice-versa, they can produce movement when a voltage is applied to them. Ferroelectric materials are already utilized in a wide array of applications ranging from positioning systems (e.g., movement of the tips on atomic force microscopes) to energy harvesting (e.g., producing electric current from shoes during walking). This project will explore new ways to control the behavior and properties of ferroelectric materials by developing new materials, referred to here as flexoelectric materials, that are ferroelectric and that are made using modern material deposition methods which produce materials that have varying amounts of atomic level strain (i.e., deformation) built into them. In other words, by depositing the materials in a very controlled way, the normal distances between atoms in the material can be changed in a desired way and this displacement of atoms from their normal equilibrium will result in changes in the material properties. The project will train the next generation of scientists and engineers who can function in a multi-disciplinary team environment and will broadly enhance the infrastructure in the United States as it pertains to the synthesis and fabrication of complex materials. The project will also utilize education and outreach programs that are designed to broaden the participation of underrepresented minorities in science and engineering.
The goal of the project is to develop new insights into how inhomogeneous strains (such as strain gradients) can be produced and used to control flexoelectric materials. In particular, scientific framework will be developed to utilize modern thin-film deposition and processing routes to expand the fundamental understanding and utilization of flexoelectric effects (the coupling between a strain gradient and electric polarization). The project will explore the nature and limits of flexoelectricity in ferroelectrics by combining design, synthesis, processing, and characterization of materials. In situ and ex situ processing methodologies will be developed to produce large and tunable inhomogeneous strains (i.e., strain gradients) via the fabrication of flexible and free-standing ferroelectric films. The program will answer two central questions: 1) how can large and deterministic strain gradients be produced, and 2) how does the presence of a large strain gradient impact the field, stress, and temperature susceptibilities of a ferroelectric material? In situ synthesis of large strain gradients in films via the production of compositional and defect gradients will be explored. Ex situ fabrication and processing methods to produce large strain gradients in substrate-supported materials will be explored, together with released and free-standing versions of materials, and the evolution of properties in materials with large strain gradients. This work will impact the fields of ferroic materials, including ferroelectric-based properties, and will have has direct impact on devices that utilize ferroelectrics including memory and logic, sensors and actuators, thermal and energy conversion applications.
