Caltech Young Investigator Lecture

Webinar Link:

https://caltech.zoom.us/j/95708772987

Webinar ID: 957 0877 2987

Abstract:

Many technologically relevant materials are not in a true thermodynamic minimum but can still be synthesized under the right conditions. Synthesizability is still difficult to predict a priori and targeting a particular phase can be further complicated by the competition between energetically similar polymorphs. In this talk I will describe how we are developing tools to predict synthesizability and processing methods to stabilize metastable materials.

Quenching and strain stabilization are the most common methods for synthesizing metastable materials, but not every phase is accessible by these methods. For example, in order to access an ordered phase with a larger volume than the ground state, we used heterostructural alloying to induce enthalpic stabilization in Mn(Se,Te). Or for phases with narrow processing windows, we turned to size stabilization to capture the desired phase. Where substrate induced strain stabilization can be used, we have developed a substrate picker tool to search through the Materials Project database for substrates that will preferentially stabilize a desired phase. Theory guided substrate epitaxy and beyond equilibrium deposition rates allowed us to realize the theoretically predicted piezoelectric P4mm phase of SrHfO3, a high energy polymorph in competition with four other known structures.

Using a theory guided approach, we have develop processing methods based on size, deposition rate, strain, enthalpy, and topotactic stabilization. A model system will be described for each method (TiO2, VO2, Mn(Se,Te), SrHfO3), showcasing where these approaches do and do not work. Many of these materials have enhanced or unique functionalities such as ferroelectricity in metastable P4mm SrHfO3 and piezoelectricity in metastable Mn(Se,Te), highlighting the importance of exploring metastable phase space.

More about the Speaker:

Lauren Garten is currently a Jerome and Isabella Karle Distinguished Scholar Fellow at the Naval Research Lab (NRL), where she works on multiferroic materials and devices. Previously she was a National Research Council Fellow of the National Academies of Science, Engineering, and Medicine who was hosted at NRL. Prior to that she did a post-doc at the National Renewable Energy Laboratory with Dr. Dave Ginley working on metastable materials for energy applications. She received her Ph.D. in material science from the Pennsylvania State University with Prof. Susan Trolier-McKinstry, focusing on piezoelectric, ferroelectric, and dielectric materials and characterization. Her undergraduate education is from the University of Missouri-Rolla (now the Missouri University of Science and Technology) in ceramic engineering. Her work focuses on the development of new materials for energy and electronic applications, particularly at the nexus between ferroelectricity, ferromagnetism, electronics, and photovoltaics.

This lecture is part of the Young Investigators Lecture Series sponsored by the Caltech Division of Engineering & Applied Science.