Dramatically improved optical anisotropy by realizing stereochemically active lone pairs in a sulfate system, K2SO4•HIO3

초록

Obtaining sulfate-based materials with large birefringence is of great challenge due to the weak polarizability anisotropy of the constituting spherical SO42- tetrahedron. Here, we have implemented a polyhedron of stereoactive lone pair cations, IO3- to the system to tackle the issue. Centimetre-sized single crystals of an alkali metal sulfate iodate, K2SO4 center dot HIO3, have been readily grown by an accessible solution-evaporation method. Optical measurements on K2SO4 center dot HIO3 single crystals reveal that the reported material exhibits a 70-fold increase in birefringence (ca. 0.14 at 589.3 nm) compared to that of the singular sulfate, K2SO4. In addition, K2SO4 center dot HIO3 exhibits a blue-shifted UV cutoff edge of 275 nm, 25 nm shorter than that of alpha-HIO3, highlighting the key role of the SO42- tetrahedron in broadening the transmittance window.

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