CsY(SO)·4HO: A Deep-Ultraviolet Birefringent Crystal Induced by an Edge-Sharing Connection.

SO tetrahedral groups have weak polarization anisotropy, which thus results in the small birefringence of sulfates. Here, we report new sulfate CsY(SO)·4HO with unprecedented birefringence among deep-ultraviolet (deep-UV) sulfates. Its single crystal (10 mm × 3.