Two Ultraviolet Optical Crystals K 6 B 12 O 19 F 4 and K 12 B 28 O 48 : The Effects of Metal Cations Size and the F Ions on the Structure.

Borates and fluorooxoborates are advanced optical materials with great potential applications in the ultraviolet (UV) and deep ultraviolet (DUV) regions. Herein, two new UV optical crystals K 6 B 12 O 19 F 4 and K 12 B 28 O 48 were synthesized. Among them, K 6 B 12 O 19 F 4 has a rare disorder of BO 3 and BO 4 units, which is the first time this disordered type has been found in fluorooxoborates. In this paper, the properties of K 6 B 12 O 19 F 4 and K 12 B 28 O 48 were tested and calculated, and their crystal structures and structural evolution were carefully analyzed. In addition, the effects of metal cations size and F ions on the crystal structure were analyzed. This research enriches the structural chemistry of borates and fluorooxoborates, and provides experience for the design of new UV optical crystals.