Borosilicates have attracted much attention due to their many potential applications and abundant new structural types from the combination of the flexible coordination geometries for both B and Si atoms. As is known to all, inorganic compounds with polar coordination units are more likely to display NCS structures and exhibit good SHG properties. It has been proved to be fruitful in obtaining polar structures by inclusion of an asymmetric salt unit as well as monatomic halide anions as a template. 

In order to design and discover new NLO crystals, approaches by the inclusion of the acentric salt units as polar template are often adopted. Recently, Professor PAN Shilie and his team from Xinjiang Technical Institute of Physics & Chemistry, Chinese Academy of Sciences (XTIPC), designed and synthesized two new salt-inclusion compounds, Ba₄(BO₃)₃(SiO₄)·Ba₃X (X = Cl, Br), which are based on the combination of two different anionic groups (SiO₄ and BO₃) and the utility of XBa₆ (X = Cl, Br) polar template (Fig.1). It is worth to note that they are the first alkaline-earth metal borosilicate halides as nonlinear optical (NLO) materials. They have SHG responses similar to that of KH₂PO₄ (KDP) and are type-I phase-matchable. In addition, they melt congruently and exhibit a wide transparent region with the UV cut-off edge below 190 nm. These properties make Ba₄(BO₃)₃(SiO₄)·Ba₃X potential deep UV NLO materials.