LiSc(SeO3)(2)center dot xH(2)O (0 <= x <= 1): New Selenites Revealing Water Molecule-Driven Extremely High Temperature Single-Crystal-to-Single-Crystal Transformations

초록

Water molecule-driven reversible phase transitions up to 450 degrees C have been observed for the first time in a novel selenite crystal, LiSc(SeO3)(2)center dot H2O, through single-crystal-to-single-crystal (SCSC) transformations. Single crystal X-ray diffraction suggests that LiSc(SeO3)(2)center dot H2O (P2/c) transforms to LiSc(SeO3)(2)center dot 0.5H(2)O (P (1) over bar), LiSc(SeO3)(2)center dot 0.25H(2)O (P (1) over bar), and alpha-LiSc(SeO3)(2) (I-42d) at 170-190, 200-230, and 240-450 degrees 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 degrees C results in a remarkably stable beta-LiSc(SeO3)(2) (R (3) over bar).

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