Imaging Octahedral Superlattices
Tailoring local oxygen octahedral structures is proving a powerful approach for the development of materials with new functionalities. However, characterizsation of locally varying octahedral structure is extremely difficult, if not impossible. This problem is epitomised by an intense controversy regarding the so-called "chessboard" nanodomain structure in the Li-ion conductor - Li0.5–3xNd0.5+xTiO3 (LNT) – a promising new generation battery material.
In the present work, a new electron microscopy imaging mode was developed (in MCEM) which can map oxygen octahedral tilt, cell-by-cell. This new method was applied to LNT to reveal and quantify the real-space topology of the octahedral structure and the resulting strain, identifying the origin of the controversial nanodomain image contrast. Remarkably, the method revealed a reversible annihilation and reconstruction of the octahedral superstructure correlated with Li-ion transport in this promising Li-ion conductor.