NaRbB3O4F3: A New Fluorooxoborate with a Short UV Cutoff Edge Enriching the Structural Chemistry of Borate

The combination of RbB3 O4 F2 and NaF generates a new member of fluorooxoborates, NaRbB3 O4 F3 , with a wide transparency range from the IR to DUV region. NaRbB3 O4 F3 shows a three-dimensional (3D) structure composed of 1D [B3 O4 F3 ]∞ chains, [NaO3 F3 ] and [RbO5 F5 ] polyhedra. The structural evolution from NaRbB3 O4 F3 to RbB3 O4 F2 , as well as the structural comparison between NaRbB3 O4 F3 and its identical stoichiometry compound, Li2 B3 O4 F3 were discussed in detail. The IR spectrum verifies its structural validity. The spectral measurement shows that the reflectance has no obvious change in the range of 175-300 nm, and its cutoff edge is below 175 nm. In addition, theoretical calculations are carried out to understand its electronic structure and optical properties.