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Download Voltage and light bring life to metal oxides Juergen Fleig Abstract
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Voltage and light bring life to metal oxides Juergen Fleig Abstract: Metal oxides find broad application in very different fields of technology including energy conversion and (micro-)electronics. They are used as electrodes and electrolytes in electrochemical cells (fuel cells, electrolyzers) but also in resistive switching devices. Further examples include piezoelectric ceramics in actuators and semiconductors for varistors or sensors. Many of those metal oxides are mixed ionic and electronic conductors, at least to a certain degree. This mixed conductivity plays a functional role in numerous applications (e.g. in fuel cells or ReRAMs) but may also lead to severe degradation of devices in other cases. An in-depth understanding of point defects in metal oxides, causing ion transport, and of the role of defects in electrochemical reactions is therefore of vital importance. Voltage and light are two important drivers of defect chemical processes or solid state electrochemical reactions in metal oxides and this talk gives an overview of multiple defect related phenomena in oxides that are caused by voltage or light. For example, a voltage affects the width of reaction zones of solid state electrochemical electrodes, leads to unusual electrode migration in PZT, triggers metallic Fe formation on LaFeO3 surfaces or modifies local conductivities in SrTiO3 thin films. Similarities are emphasized between oxides used in different fields, e.g. in piezo actuators and solid oxide fuel cells. The effect of light on defect chemical processes, on the other hand, is essential when aiming at solid state photoelectrochemical cells. An oxide based high temperature solar cell, operating at >400°C, is introduced which can be used to chemically store energy. Moreover, oxygen stoichiometry changes in SrTiO3 under UV illumination lead to a voltage in an electrochemical cell and thus the charging of a kind of battery by light could be realized. Bio: Juergen Fleig is Professor of Electrochemistry at Vienna University of Technology (Austria). Fleig received his diploma degree in Physics from University of Tuebingen (Germany) and did his PhD research at Max Planck Institute of Solid State Research, Stuttgart (Germany), receiving the PhD degree in Chemistry in 1995. Subsequently, he worked as researcher at the same Max Planck Institute and lectured at University of Ulm (Habilitation degree in 2002 in Physical Chemistry). After research stays at Massachusetts Institute of Technology, Cambridge (2002-2003), University Tor Vergata Rome (2003) and again Max Planck Institute for Solid State Research he was offered the Chair of Electrochemistry in Vienna (2005) which he holds until now. Fleig's research has centered on several aspects of defects, ion motion and reaction in solids, with emphasis on materials used in energy technology (fuel cells) and as dielectrics or piezoelectrics. This includes development of novel experimental tools for analyzing local ionic conductivities by microelectrodes or mapping reaction zones of gas-solid interfaces by tracer ions. Further research dealt with the basic understanding of impedance spectroscopic data and the kinetics of electrochemical reactions in solids. These scientific activities brought recognition by the American Ceramic Society (Edward C Henry Awards) and the International Society of Electrochemistry (Tajima Prize).
