Ba4(BO3)3(SiO4)·Ba3X (X = Cl, Br): new salt-inclusion borosilicate halides as potential deep UV nonlinear optical materials

Abstract

Based on the combination of two different anionic groups (SiO₄ and BO₃) and the utility of a XBa₆ (X = Cl, Br) polar template, two new salt-inclusion compounds, Ba₄(BO₃)₃(SiO₄)·Ba₃X (X = Cl, Br) have been successfully synthesized by the high-temperature solution method for the first time. They are isostructural and their structures feature the _∞³[Ba₄(BO₃)₃(SiO₄)] framework with 1D channels along the c axis, in which resided the polar _∞¹[Ba₃X] chains. It is worth noting that they are the first alkaline-earth metal borosilicate halides to be used as nonlinear optical (NLO) materials. The second harmonic generation (SHG) measurements show that 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.