FLAIR: A New Research Center on Fermi Level Engineering of Oxide Electroceramics
KLEIN A. 1
1 Technical University of Darmstadt, Darmstadt, Germany
Chemical substitution, which can be iso- or heterovalent, is the primary strategy to tailor material properties. There are various ways how a material can react to substitution. Isovalent substitution changes the density of states while heterovalent substitution, i.e. doping, can induce electronic compensation, ionic compensation, valence changes of cations or anions, or result in the segregation or neutralization of the dopant. While all these can, in principle, occur simultaneously, it is often desirable to select a certain mechanism in order to determine material properties. Being able to predict and control the individual compensation mechanism should therefore be a key target of materials science. This contribution outlines the perspective that this could be achieved by taking the Fermi energy as a common descriptor for the different compensation mechanisms. This generalization becomes possible since the formation enthalpies of the defects involved in the various compensation mechanisms do all depend on the Fermi energy. In order to control material properties, it is then necessary to adjust the formation enthalpies and charge transition levels of the involved defects. Understanding how these depend on material composition will open up a new path for the design of materials by Fermi level engineering. This is the target of the research center FLAIR, which has been established in January 2023 by the German Research Foundation. In this center, research groups at the Technical Universities of Darmstadt and Graz, the University of Stuttgart, and the RWTH Aachen university will establish the foundation of Fermi level engineering of oxide electroceramics.