BaAlPO 4 F 2 : structure and properties of the first barium fluoroaluminophosphate with the mixed anion group [Al 2 PO 8 F 5 ]

The first barium fluoroaluminophosphate BaAlPO 4 F 2 was synthesized possessing a short cutoff edge (<200 nm) and suitable birefringence. BaAlPO 4 F 2 presents the unusual [Al 2 PO 5 F 4 ] ∞ 2D layers formed by [PO 4 ], [AlO 2 F 4 ] and [AlO 2 F 4 ].