The crystal structure of LiSc2SbO6

The crystal structures of LiM2SbO6 (M ​= ​Sc, Fe, Mn, In) were originally described as ordered, Pnn2 variants of the Pnna LiSbO3 structure. Recently, however, a single crystal study on the M ​= ​In analogue revealed that its structure is better described as rutile-related with alternating-width chains and Pnnm symmetry. Here, the structure of LiSc2SbO6 (M ​= ​Sc) is similarly revisited with single crystal X-ray diffraction which indicates that it is an Li-ordered variant of the LiIn2SbO6 (M ​= ​In) structure with polar Pmn21 symmetry and a Flack parameter value of 0.5. Solid-state NMR confirms that Li is tetrahedrally coordinated, a key difference between the ordered LiSbO3 and rutile-related models structures. Differential thermal analysis reveals a second-order phase transition between 460 and 480 ​K. With this context, the implications of the low-temperature Flack parameter and powder diffraction data are discussed.