Two Short-Wave UV Antimony(III) Sulfates Exhibiting Large Birefringence.

In the present work, we have successfully obtained two new UV antimony-based sulfates, NH 4 Sb(SO 4 ) 2 and Ca 2 Sb 2 O(SO 4 ) 4 , by a conventional hydrothermal method. Interestingly, both compounds share similar structural building blocks, such as SbO 4 seesaws and SO 4 tetrahedra, yet they endow discrepant birefringence values measured at 546 nm with values of 0.150 and 0.114, respectively, owing to the different distortions of the SbO 4 groups with SCALP electrons. Moreover, both compounds display large band gaps (4.32 and 4.43 eV, respectively), so they can be used as short-wavelength UV birefringent materials. Moreover, NH 4 Sb(SO 4 ) 2 is a noncentrosymmetric compound, showing a frequency doubling effect of 0.2 × KDP. Detailed structural analyses and calculations confirm the source of superior optical performance and the reasons for the different birefringence of the two compounds. This work provides ideas for the following discovery of antimony-based optical materials with excellent properties.