Materials for Electronics & Photonics
KAdvanced Doping Strategies, Defect States and Electronic Structure of Functional Oxides - 27
Chemical substitution, iso- or heterovalent, is fundamental for tailoring material properties. While such strategies are well established in classical semiconductors, they remain poorly understood in functional oxides due to the greater complexity of defect formation and charge-compensation mechanisms. A broad exchange within the scientific community, including discussion of the role of the electrochemical potential of the electron (Fermi level), is needed to advance understanding of the underlying physics and chemistry and ultimately enable control over material properties.
Scope:
Functional oxides play a crucial role in many energy technologies related to the energy transition and efficient energy conversion and storage. Examples include the reversible exsolution/segregation of oxide-based heterogeneous catalysts for three-way catalysis or water (photo)electrolysis, reversible lithium uptake and release in cathode materials, dielectric and piezoelectric materials for sensors and actuators, high-temperature thermoelectrics for electricity generation from waste heat, and mixed ionic–electronic conducting ceramic membranes for O₂ or H₂ separation and transport. A common strategy to tune their functional properties is iso- or heterovalent (partial) substitution, the latter commonly referred to as doping.
However, all these materials share a common challenge: doping strategies are largely defined empirically, and it remains unclear how to a priori select and process suitable host materials and dopants to reproducibly achieve the intended material properties, as has long been established for classical semiconductors. This difficulty arises from the various ways in which materials can respond to doping, including electronic compensation, ionic compensation, valence changes of cations or anions, and the segregation or neutralization of dopants.
This symposium therefore aims to bring together a broad range of expertise to work toward an overarching and potentially predictive concept. A unifying framework may be the description of the aforementioned charge-compensation mechanisms and defect formation on a common energy scale, namely the Fermi level. Understanding the allowed energetic ranges of the Fermi level and their transferability between systems could ultimately enable data-driven prediction of doping strategies.
Key requirements for the successful development of such a concept are close interaction and the establishment of a unified terminology to describe the same phenomena from different perspectives. This includes expertise in solid-state and defect chemistry, semiconductor physics, materials and defect modelling, spectroscopic techniques—particularly X-ray photoelectron spectroscopy—as well as the investigation of locally resolved defect effects, for example by transmission electron microscopy, and knowledge of the major application fields of functional oxides.
Hot topics to be covered by the symposium:
- New synthesis routes for doped oxides with defined & reproducible properties
- Doping concepts for oxides to advance material properties
- Cationic versus anionic substitution
- Interface properties of electroceramics
- Ex-solution & segregation behavior of catalysts/electrodes
- Latest developments in defect modelling on different length & time scales
- Transport and surface reaction kinetics of mixed ionic-electronic/triple-conducting ceramics, e.g., oxygen & hydrogen separation/transport membranes
- Recent advances of spectroscopic characterization methods including in-situ & operando approaches
- Influence of the thermodynamically allowed Fermi level range and its role for the defect chemistry
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C/ Sor Juana Ines de la Cruz, 3, 28049, Madrid, Spain
ainara.aguadero@csic.esInstitute of Materials Science, Peter-Grünberg-Straße 2, 64287 Darmstadt, Germany
marc.widenmeyer@mr.tu-darmstadt.deInstitute of Physical Chemistry, Landoltweg 2, 52056 Aachen, Germany
desouza@pc.rwth-aachen.de1-10-1, Higashikotari, Nagaokakyo, Kyoto 617-8555, Japan
h_sakyo@murata.com