PbTeB 4 O 9 : a lead tellurium borate with unprecedented fundamental building block [B 4 O 10 ] and large birefringence.

Herein, the first lead tellurium borate, PbTeB 4 O 9 , with an unprecedented fundamental building block [B 4 O 10 ] was successfully synthesized. The near-parallel alignment of [B 4 O 10 ] groups and [TeO 3 ] polyhedra resulted in a high birefringence (0.099@1064 nm). The structure-property relationship was discussed by using the first-principles calculations.