LiSc(SeO3)2·xH2O (0 ≤ x ≤ 1): New Selenites Revealing Water Molecule-Driven Extremely High Temperature Single-Crystal-to-Single-Crystal Transformations

Water molecule-driven reversible phase transitions up to 450 °C have been observed for the first time in a novel selenite crystal, LiSc(SeO 3 ) 2 ·H 2 O, through single-crystal-to-single-crystal (SCSC) transformations. Single crystal X-ray diffraction suggests that LiSc(SeO 3 ) 2 ·H 2 O ( P 2/ c ) transforms to LiSc(SeO 3 ) 2 ·0.5H 2 O ( P 1̅), LiSc(SeO 3 ) 2 ·0.25H 2 O ( P 1̅), and α-LiSc(SeO 3 ) 2 ( I –42 d ) at 170–190, 200–230, and 240–450 °C, respectively. The structural evolution is attributable to the different positions of Li + cations within the eight-membered ring (8-MR) channel, in which the amount of water molecules plays a key role in determining the coordination environment and the subsequent location of Li + cations. Further heating of the crystal to 500 °C results in a remarkably stable β-LiSc(SeO 3 ) 2 ( R 3̅).