Collaborative Research: Martensitic Transformations in Paraelectric Shape Memory Ceramics Activated by an Electric Field

点击翻译按钮获取中文摘要

Non-Technical SummaryA martensitic transformation is a structure change that takes place in some crystalline materials, in which the atoms spontaneously and rapidly reshuffle into a new crystal structure in a coordinated way. In some materials this transformation is reversible, so that the material can repeatedly transform back and forth between two shapes, giving rise to the property of “shape memory”. In a martensitic ceramic like zirconia, the shape change is very large (elongating and contracting a shape by ~10%) and it also exerts very large forces. For this reason, shape memory materials are like “solid-state engines”, able to do work on their surroundings as actuators. What is more, it has been recently discovered that shape memory zirconia can be transformed by applying electric fields to it, which opens the door to electronic control over shape memory. With support from the Ceramics Program in the Division of Materials Research, this project investigates the new property of electrical shape memory in ceramics and develops tools to discover and design new ceramic materials that exhibit this property. The project consists of computational and theoretical efforts to understand how different parameters affect the martensitic transformation, led by Prof. Homer at Brigham Young University, and an experimental effort to validate the phase transformation theory for different orientations of the crystals, temperatures, and applied electric fields. This research to synthesize and test new prospective shape memory ceramics is carried out in Prof. Schuh’s research group at the Massachusetts Institute of Technology. This research has implications for actuator device technologies, which have not been as easily miniaturized as other electronic technologies. Additionally, the project will also provide scientific training for two PhD students, one at each institution, and outreach activities will involve a collaborative effort to strengthen the roll out of a Materials Science minor program at BYU to unify materials-oriented students that are spread across different majors on campus.Technical SummarySupported by the Ceramics Program in the Division of Materials Research, this project investigates a new class of shape memory ceramics in which the classical advantages of shape memory (the ability to do large amounts of mechanical work through a solid state phase transformation) are paired with a new mechanism for activating that property (an electric field-driven paraelectric-to-paraelectric phase transformation). Besides developing an entirely new class of “paraelectroactive” ceramics that can perform meaningful mechanical work and expanding the portfolio of electroactive ceramics, the research also has implications for the theory of phase transformations more broadly. The research involves four interrelated tasks: (1) developing and validating thermodynamic models that incorporate the coupled influence of electrical-thermal-mechanical energy on a paraelectric-to-paraelectric martensitic transformation; (2) examining the role of crystal orientation and anisotropic material properties on the predicted and observed phase transformation conditions; (3) exploring the role of dopants to control the transformation conditions and enable room temperature operation of this phenomenon; (4) expanding the materials-scope of the phenomenon by discovering alternative (non-zirconia) shape memory ceramics that exhibit paraelectric-paraelectric martensitic transformations. These tasks are collaboratively investigated with a primarily experimental effort in Prof. Schuh’s research group at the Massachusetts Institute of Technology and Prof. Homer’s research group mostly carrying out theoretical effort at Brigham Young University.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.