Borates have a large structural variety and occur in many minerals. They can, for example, be used to create specialized glasses with high UV transmittance. Alkaline earth metal borates, e.g., barium borates, are particularly promising for this type of application. Their properties can be tuned by replacing some oxygen atoms with halides, leading to barium borate halides.

S. L. Pan, H. H. Yu, Xinjiang Technical Institute of Physics & Chemistry, Chinese Academy of Sciences, Urumqi, China, and colleagues have synthesized a new barium borate halide, Ba₃B₁₀O₁₇Br₂. The team used a solid-state reaction in a sealed system to combine BaF₂, KBr, and B₂O₃ and obtained single crystals of Ba₃B₁₀O₁₇Br₂.

The product was characterized using single-crystal X-ray diffraction. The team found that the compound features a (B₁₀O₁₇)_∞ double-layer structure, bridged by Ba atoms (pictured). According to the researchers, the compound is the first barium borate halide with a 2D B–O layered structure. Previously reported barium borate halides are composed of either isolated B–O groups or 3D B–O frameworks.

• Ba₃B₁₀O₁₇Br₂: a new barium borate halide with B–O layered structure,
  S. J. Han, H. P. Wu, H. Li, Z. H. Yang, S. L. Pan, H. H. Yu,
  Dalton Trans. 2018, 47, 16418–16421.
  https://doi.org/10.1039/c8dt04052d