X-ray Methods for Structural and Phase Analysis
Our team is focusing in implementation of the state-of-the-art X-ray methods for the main aspects of structural, phase and chemical states analyses by means of home-lab and synchrotron based methods. These methods are currently presented in our team by powder and single crystal X-ray diffraction (PXRD and SCXRD), methods of X-ray small angle scattering (SAX), methods of X-ray photoelectron spectroscopy (XPS), and advanced synchrotron methods, such as X-ray absorption near edge spectroscopy (XANES in different modes - HERFD, RIXS, XES) and EXAFS. We apply these methods in ex-situ as well as in in-operando modes.
Investigation of Phase Stability / Purity
Materials chemical/phase purity play a crucial role in advanced energy materials properties. For a precise analysis of phase purity, we use methods of classical powder diffraction (PXRD). We are well equipped with two PXRD machines with which we can access the phase purity characterization up to 0.5 % weight. The measurements can be performed in both transmission and reflection modes, on powder or microfilm samples. For determination of phase stability we can run XRD experiments under elevated temperature (HT-XRD) or/and controlled atmosphere (humidity/gases content). The HT-XRD experiments can be performed on powder samples (HT-PXRD up to 1000°C) or on single crystalline samples (HT-SCXRD up to 800°C) using our advanced Bruker D8 Venture dual source (Mo and Ag) machine. This pallet of methods allow us serial/routine as well as precise characterization of crystalline energy materials purity and their phase stability. 1 Our equipment allows us in-situ/in-operando studies of battery/electrolysers materials stability and evolution in working cells.
Investigation of Short- and Long-Range Atomic Order
The properties of the materials are in direct dependence on their atomic structures. We are conducting studies of IET-1 materials atomic structures using home lab facility for PXRD and single crystal X-ray diffraction (SCXRD). Our double source (high intense IμS Diamond Mo and Ag) state of the art SCXRD system allow precise study of very small crystals up to 5 μm.2, 3 We are using Rietveld method to study the atomic ordering in powder samples and different approaches to solve the structures from the single crystal data. For both methods (PXRD and SCXRD) we are equipped with high and low temperature devices (HT and LT) and flexible gases/humidity atmospheres. Data collection at LT in dry N2 flow is required for air and humidity sensitive samples, such as new types of sulphur- or halide-based battery materials. The above-described methods are limited for the long-range structural analysis and can give a solid structural understanding of the crystal structures of classical, non-heavily disordered, materials. For materials that are more complex, we use these data as the basic models for deeper inside into the local, so called short-range structural ordering.
For characterization of short-range ordering, we use a home lab PDF (pair-distribution function) facility and large-scale synchrotron facility (ESRF, DESY) for EXAFS (extended X-ray absorption fine structure) data collection. PDF analysis is not element specific and can provide us with the local distribution of atoms for a total structure of crystalline and non-crystalline materials. The EXAFS data are element specific and ideal for the local environment speciation of a selected element. PDF and EXAFS can also be applied to an in-situ/in-operando process for dynamic studies of structural transformations. Using both, long- and short-range approaches, we can deeply understand the atomic structures of advanced energy materials created at IET-1 and their structural evolution upon electrochemical processes.
Investigation of Chemical States / Bonding
To understand the oxidation states of chemical elements and some aspects of chemical bonding in new energy materials designed and studied at IET-1, we use home lab XPS facility and synchrotron based XANES (X-ray absorption near edge structure) techniques. 4 This is especially important for the battery and catalytic materials as the dynamic oxidation state changes upon work of an electrochemical cell. The XPS data, collected from the surface, can be amended with bulk, element-specific data of XANES experiments. For example, we show differences in pre-edge Fe-XANES high-entropy cathode materials with Mg to Ni substitution, which corresponds to the change in electronic configuration of Fe atoms in the structure. These data in combination with the data for atomic near- and long-range ordering (above) give us a full picture of phase structures and chemical states for all types of electrochemical materials designed and studied at IET-1.
Investigation of nano-/and polymer samples with SAXS techniques
The electrochemical materials, that are under study in IET-1, often exist in a form of polymer/inorganic composites, nano-particles, or micro- and mesoporous phases. In order to characterize the sizes or particles, their agglomeration, possible core/shell structures, particles surface aspects and agglomeration in polymers (for example in membranes for electrocatalysis) we use modern techniques of SAXS (small angle X-ray scattering). By using this instrumentation, we go deeply into analysis of size/form of active particles for implementation in battery and electrocatalysis. Ex-situ and post-mortem studies reveal the mechanisms of nano-particles evolution and their stability upon electrochemical cycling in the working cells. Combining with other methods (for example BET) SAXS studies are optimal for active surface characterization of electrochemical materials.
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Last Modified: 14.02.2025