Project Details
Projekt
Determining Oxidation States, Concentration Profiles, Local Coordination, and Mobilities in Solids and at Interfaces by X-Ray Photoelectron and X-Ray Absorption Spectroscopies
Applicant
Professor Dr. Michael Gottfried
Subject Area
Physical Chemistry of Solids and Surfaces, Material Characterisation
Term
since 2025
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 428906592
This project aims to determine oxidation states, concentration profiles, local coordination environments, and ion mobilities in solids and interfaces using X-ray Photoelectron Spectroscopy (XPS), Hard X-ray Photoelectron Spectroscopy (HAXPES), Near-Edge X-ray Absorption Fine Structure (NEXAFS), and Extended X-ray Absorption Fine Structure (EXAFS). As part of the second funding period of ELSICS, this research focuses on characterizing transport mechanisms and electronic structures in bulk materials and at grain or phase boundaries, with particular emphasis on amorphous solids such as glasses and crystalline perovskites. Our recent studies indicate that prior assumptions regarding the oxidation states of transported alkali metal species may be incorrect, underscoring the necessity of refining experimental techniques to reliably determine oxidation states. To address this, we will employ synchrotron-based HAXPES and NEXAFS to overcome limitations of conventional XPS, providing deeper insights into bulk properties and interfacial chemistry. The project is structured around four primary objectives: determining alkali metal oxidation states in bulk materials, understanding ion transport in bulk and at interfaces, spatially resolving perovskite phase boundaries, and studying local coordination environments using EXAFS. Investigations will focus on alkali metals in glasses such as alkali silicates and perovskites including SrTiO3, BaTiO3, and La1-xSrxMnO3. The study will be extended to single grain boundaries in homo- and hetero-bicrystals to examine oxidation state variations and their impact on transport properties. Time- and temperature-dependent HAXPES depth profiling will be employed to analyze ion transport in thin-film layered systems, while a comparison of transport properties at grain boundaries and external surfaces will elucidate structural and chemical influences on mobility. High-spatial resolution XPS at the NanoESCA beamline will be used to investigate oxidation states of transported alkali metals and other constituent elements at interfaces, assessing how ion transport modifies the local electronic and chemical environment at phase boundaries. Additionally, EXAFS will be used to characterize short-range order and local structural changes in glass samples, particularly in response to alkali metal diffusion, and the mixed alkali effect in binary silicate glasses will be explored to understand its impact on nonlinear conductivity variations. The project will employ laboratory and synchrotron-based X-ray spectroscopies to provide a comprehensive picture of oxidation states, charge transport mechanisms, and structural dynamics in complex materials. Our findings will enhance the understanding of ion mobilities and electronic structure, contributing to broader efforts in energy materials research.
DFG Programme
Research Units
