Ba 3 B 10 O 17 F 2 ·0.1KF: the first mixed alkali/alkaline-earth metal fluorooxoborate with unprecedented double-layered B-O/F anionic arrangement.

The diverse oxyfluoride species and vast number of different topological arrangements lead to fluorooxoborates' structural beauty and richness. Herein, the first mixed alkali/alkaline-earth metal fluoro-oxoborate Ba3B10O17F2 center dot 0.1KF was successfully synthesized and systemically characterized. Its most important structural feature is an unprecedented double-layered B-O/F anionic arrangement.