Li<sub>2</sub>NaB<sub>3</sub>S<sub>2</sub>O<sub>12</sub>: A Deep-UV Transparent\nBorosulfate with Moderate Birefringence Derived\nfrom the [B<sub>3</sub>S<sub>2</sub>O<sub>

The\nfirst mixed alkali metal borosulfate compound, Li<sub>2</sub>NaB<sub>3</sub>S<sub>2</sub>O<sub>12</sub> (LNBSO), which contains\n[BO<sub>3</sub>] groups, was designed and synthesized by using a high\nboron-to-sulfur ratio strategy through the high temperature solution\nmethod. LNBSO exhibits a birefringence of [email protected] nm in experiments,\nwhich was mainly contributed by the [BO<sub>3</sub>] groups, and possesses\na short absorption edge at 184 nm, and the space group of LNBSO is <i>P</i>2<sub>1</sub>/<i>c</i>. This newly synthesized\nborosulfate compound holds potential as a promising birefringent material\nwithin the deep-ultraviolet wavelength range. Moreover, the investigation\non the relationship among the ratio of boron to sulfur, the dimensionality\nof the anionic framework, and the formation of [BO<sub>3</sub>] groups\nhas been conducted on available borosulfate, providing insights for\nthe synthesis of borosulfate with desirable performances.