An Antimony(Iii) Borate With Large Birefringence Exhibiting Unwonted [B5o11] Fundamental Building Blocks And Dimeric [Sb2o6] Clusters

A new birefringent crystal SbB5O9 has been synthesized by combining pi-conjugated [B3O6] groups and Sb3+ cations with SCALP. It exhibits the unwonted [B5O11] fundamental building block (FBB) and dimeric [Sb2O6] cluster. Remarkably, SbB5O9 exhibits a short UV cutoff edge (below 240 nm) and a large birefringence (Delta n = 0.151 @ 1064 nm) which is even better than that of the well-known commercial birefringent material alpha-BaB2O4 (alpha-BBO) (Delta n = 0.122 @ 532 nm). First-principles calculations show that the birefringence enhancement mainly originates from the highly distorted [Sb2O6] dimer and pi-conjugated B-O anionic groups.