BaZnBe2(BO3)2F2: a novel zinc-beryllium borate with SBBO-type structure overcoming the polymorphism problem.

A novel zinc-beryllium borate BaZnBe2(BO3)2F2 was grown by a high-temperature flux method for the first time. It crystallizes in P with the cell parameters of a = b = 4.5998, c = 7.7037 and Z = 1, which is different from BaMBe2(BO3)2F2 (M = Mg, Ca). Interestingly, when Zn replaces Mg and Ca in BaMgBe2(BO3)2F2 and BaCaBe2(BO3)2F2, the structure retains the same anionic group but the symmetry is lowered. The title compound contains a flexible net structure [Be3B3O6F3]∞ in the a–b plane with Ba and Zn atoms located in the interlayers accordingly, which overcomes the structural instability problems of SrBe2B2O7 (SBBO). The structure evolution from SBBO to BaZnBe2(BO3)2F2 was discussed. This work is of great significance to the discovery of new materials and the modification of existing materials.