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Diffraction Based Transmission X-ray Microscopy

Final Report Summary - D-TXM (Diffraction Based Transmission X-ray Microscopy)

Crystalline materials are ubiquitous: examples are metals, ceramics, semiconductors, rocks, ice,
sand, bones and many artefacts of artistic and archaeological interest. They tend to be composed of elements such as grains and domains that are structured hierarchically in a complex manner on
several length scales. In materials science and geoscience, major research efforts are directed at
establishing multi-scale models that predict the evolution of the entire structure during materials transformations such as processing or failure. At present, however, rigorous bottom-up
approaches are not computationally feasible, and coarse-scale modelling of average properties often fails as special events, such as the nucleation of new grains or cracks tend to govern the structural evolution. As a result, state-of-the art models at best systematize generic features of the static structure. Simultaneous inspection of the structural dynamics inside crystalline materials on multiple length scales and in three dimensions (3D) would therefore be a major step forward, in terms of guiding and verifying such modeling efforts.

In the d-TXM project we have developed transmission dark-field X-ray microscopy; a
non-destructive microscopy technique for the three-dimensional mapping of grains, domains,
defects, orientations and stresses within embedded sampling volumes of mm sized samples. Using x-ray lenses as condensers and objectives, the technique allows 'zooming' in and out. It is a full-field imaging technique in which the camera records the image of an entire layer or an entire projection of a volume within the sample, enabling fast data acquisition. The angular resolution can be as good as 0.001 deg.

A first generation d-TXM microscope is built at the European Synchrotron Radiation Facility, ESRF in Grenoble. The resolution is currently 30 nm, which is an improvement of nearly two orders with respect to existing methods. Commissioned end 2016, the instrument immediately was seen as a success. Based on first results ESRF decided to prioritize a second generation instrument as one of four flagship projects for the ESRF upgrade infrastructure, EBS. The new instrument is specified to have a 100-1000 times increase in performance.

As examples of materials science studies performed with the microscope we mention:

- In situ annealing studies of plastically deformed Al has revealed new mechanisms controlling the process of recrystallization
- d-TXM provides fascinating new possibilities for 3D imaging of defects in semiconductors at a much improved spatial resolution.
- For the first time the deterioration of a functioning fuel cell has been observed at the scale of the individual grains within the electrodes.
- Uniquely d-TXM provides a direct means to make 3D movies of the domains within functional ceramics. Studies on oxide ferroelectrics have revealed a major gap in our understanding of these materials: intrinsic defects create strain fields that extend a thousand times further than previously thought. Given that these defects have a profound effect on properties, this opens an entirely new paradigm for understanding and realizing the full potential of engineering defects and with it, a new generation of ferroelectric materials.