Peering into the Hidden Defects of Crystals in 3D

Mapping V₂O₅ catalyst in 3D

We demonstrated XL-DOT on nanoporous vanadium pentoxide (V₂O₅), a material of high industrial importance as a catalyst. With a spatial resolution in 3D of just 73 nanometres, we were able to differentiate individual grains, determine their crystallographic orientation, and distinguish between single-crystalline and polycrystalline regions that appear identical in conventional tomography.

The reconstructions revealed a rich assortment of grain shapes, with elongated single crystals spanning micrometres and smaller nearly spherical grains clustered in dense regions, and clear correlations between size and morphology. Importantly, XL-DOT allows us to identify grain boundaries with misorientation angles down to approximately 10°C, providing detailed insights into the microstructural fabric of the material.

Visualizing crystallographic and topological defects

Beyond grains and boundaries, our method reveals intricate defect structures within the crystal lattice. We resolved twist, tilt, and twin boundaries as well as more exotic topological defects, including comet and trefoil configurations. We could track their creation, motion, and annihilation through the sample in the presence of structural voids, obtaining important insights into how defects evolve during material processing. 

Importantly, XL-DOT is not limited to vanadium oxides — it can also be applied to a broad class of materials that exhibit linear dichroism, including antiferromagnets and ferroelectrics. These materials are of particular interest for low-power-consumption, next-generation electronic devices, where controlling magnetic and electric order at the nanoscale is key.

Towards operando 3D imaging

Bridging the gap between high-resolution electron microscopy and lower-resolution X-ray techniques, XL-DOT enables the non-destructive nanoscale 3D characterisation of sample volumes that are large enough to be representative of the material under investigation. The spectroscopic nature of XL-DOT opens exciting opportunities for operando experiments, where both composition and microstructure can be tracked under changing temperature or chemical conditions.

With the next generation of synchrotron sources, even higher spatial resolutions and faster acquisition times are expected to be achieved. This will extend XL-DOT to a wide range of crystalline, magnetoelectronic, and soft materials, advancing our ability to link nanoscale structure to macroscopic function.