Benchmarking 3D electron diffraction strategies for ceramics

Three-dimensional electron diffraction (3D ED) became increasingly popular over the last two decades, challenging the limits of established single-crystal X-ray diffraction experiments. In particular continuous-rotation and precession-assisted protocols were established as important tools in the collection of electron diffraction data, most of the nowadays solved crystal structures by 3D ED being acquired with one of both methods. This stands further true for ceramic materials, where 3D ED allows deep insights into complex structure-property relationships. As ceramic syntheses tend to yield thick and highly crystalline particles, one bottleneck in the refinement against electron diffraction data are coherent inelastical scattering effects. While dynamical refinement procedures allow the simulation of multiple scattered electrons, they in general ignore the inelastic contribution. This work aims, inter alia, to evaluate the impact of dynamical inelastic effects on the diffraction data of ceramics and their overall quality dependent on the operated measurement strategy. This was done by comparing the structure models derived from the same crystal under similar experimental conditions of three ceramic compounds, namely NATP (Na1+xAlxTi2-x(PO4)3), LATP (Li2-xAlxTi2-x(PO3)4) and almandine (Fe3Al2[SiO4]3), based on precession, continuous-rotation and stepwise static rotation electron diffraction data. The different methods allowed the detection of low-occupied mobile sodium and lithium ions in the difference electrostatic potencial maps, paving the way for future studies on their migration behaviour in solid-state electrolytes.