Na 2 SrB 16 O 26 : a new borate with independent interpenetrating B-O networks and deep-ultraviolet cutoff edge.

A new borate, Na 2 SrB 16 O 26 , was synthesized by the high-temperature solution method. It exhibits complicated interpenetrating 3D B-O frameworks composed of the functional building block (FBB) [B 8 O 16 ]. The UV-vis-NIR diffuse reflectance spectroscopy shows that it has a deep-ultraviolet (DUV) cutoff edge (<200 nm). The relationship between the structures and optical properties was uncovered by theoretical calculations. By the first-principles calculation, the birefringence is estimated to be 0.07 at 1064 nm. The response electron distribution anisotropy (REDA) analysis indicates that the [BO 3 ] units contribute mainly to the generation of the moderate birefringence.