Conversion Processing of Functional Oxides to Oxyfluorides

Drexel University, Philadelphia PA

Investigators

Abstract

Complex oxides play a critical role in wide-ranging technologies that underpin modern society with applications in the energy, communications, and health sectors. The ability to make thin films of these materials will enable new applications in electronics and energy conversion. However, in order to fully harness the potential of oxide films, new processing approaches are required that will enable a wider range of material compositions to be manufactured. This award supports fundamental research focused on developing and understanding strategies for the controlled substitution of fluorine for oxygen, thereby enabling new means to engineer electronic, optical, and magnetic properties of thin films and nanomaterials. The processing methods to be studied are scalable, require minimal capital investment, and can be carried out on a broad range of oxide films, independent of how the materials were first processed. As such, the research will directly support the nation's strategic goal of developing agile new approaches for materials processing that can reduce the time from material discovery to technological deployment. The research will also benefit the U.S. economy by contributing to the advanced engineering education of the participating students. While advances in deposition techniques have enabled the processing of perovskite oxide films with monolayer precision, expanding access to new material chemistries remains a challenge. This project is focused on the substitution of fluorine for oxygen, which allows for control of the transition metal cation valence state and the covalency of the metalanion bond, both effects having profound implications for electronic, ferroic, and optical properties. This research will elucidate fundamental scientific mechanisms in the synthesis of oxyfluoride mixed-anion perovskites based on post-growth conversion reactions of oxide films. The conversion processes to be studied utilize vapor transport and anion diffusion from fluoropolymers. The team will deposit oxide films, carry out fluorination reactions, and utilize spectroscopic and structural characterization techniques to develop a predictive understanding of how the resultant anion composition can be engineered through processing conditions to tune functional properties.