Benchmarking 3D electron diffraction strategies for ceramics

Three-dimensional electron diffraction (3D ED) has become 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 have been established as important tools in the collection of electron diffraction data, and the data for most of the crystal structures solved by 3D ED nowadays are acquired with one of these two methods. This is particularly 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 issue in the refinement against electron diffraction data is the effect of coherent inelastic scattering. While dynamical refinement procedures allow the simulation of multiple scattering events, in general they ignore the inelastic contribution. This work aims to evaluate the impact of dynamical inelastic effects on the diffraction data of ceramics and how their overall quality depends on the measurement strategy used. This was done by comparing the structure models derived from the same crystals under similar experimental conditions of three ceramic compounds, namely NATP [Na_1+xAl_xTi_2-x(PO₄)₃], LATP [Li_2-xAl_xTi_2-x(PO₃)₄] and (Fe₃Al₂[SiO₄]₃), based on precession, continuous-rotation and stepwise static tilt data. The different methods allowed the detection of low-occupancy sites in the difference electrostatic potential maps corresponding to mobile sodium and lithium ions, paving the way for future studies on their migration behaviour in solid-state electrolytes.