BaZn3(BO3)2F2: a new beryllium-free zincoborate with a KBBF-type structure

Abstract

A new beryllium-free zincoborate, BaZn₃(BO₃)₂F₂, with a KBBF-type structure has been synthesized for the first time. The electrostatic force of interaction in BaZn₃(BO₃)₂F₂ provides better linkage in neighboring [ZnBO₃F]_∞ single layers. BaZn₃(BO₃)₂F₂ is the first case of borates with both [ZnO₃F] tetrahedra and [ZnO₆] octahedra, enriching the structural chemistry of borate system. All the coplanar [BO₃] triangles align in the same direction with a high density, which endows BaZn₃(BO₃)₂F₂ with a large birefringence of cal. 0.076 at 1064 nm. This work is of great significance to design beryllium-free borates with a KBBF-type structure.