Ba 5 Zn 4 (B 3 O 6 ) 2 (B 12 O 24 ): A Borate with Edge-Sharing [BO 4 ] Tetrahedral Connection by Introducing Zn into β-BaB 2 O 4

The edge-sharing connection mode of [BO 4 ] tetrahedra has greatly enriched the structural chemistry of borates, which provides more options and possibilities for designing more materials with unique structures and excellent performance. A zinc borate Ba 5 Zn 4 (B 3 O 6 ) 2 (B 12 O 24 ) (BaZnBO) was synthesized via a high-temperature solid reaction. Its uniqueness lies in not only introducing Zn into the structure of β-BaB 2 O 4 but also containing the unusual edge-sharing [BO 4 ] tetrahedra. The functional building units are isolated [B 3 O 6 ] and [B 12 O 24 ] groups. The adjacent [B 3 O 6 ] groups are linked to a layer in the ab plane and further stack along the [001] direction, while the [B 12 O 24 ] groups are located in the middle of these layers, thus forming the “sandwich” structure. This work also analyzed the impact of introducing Zn into β-BaB 2 O 4 on the structure of anions. In addition, BaZnBO also exhibits good thermal stability and excellent optical properties including the short cut-off edge (204 nm) and suitable birefringence (0.058@1064 nm).