Synthesis, structures, optical properties and electronic structures of two mixed metal borates MBaB5O9 (M = Na, K)

• Two new compounds NaBaB5O9 and KBaB5O9 were synthesized.
• The two compounds both exhibit short the UV absorption edges.
• NaBaB5O9 exhibits congruent melting property.
• The electronic structures and linear optical response are calculated.

Two ternary borates, MBaB5O9 (M = Na, K) have been synthesized by the flux method. Single-crystal X-ray diffraction analysis revealed that they crystallize in the same space group P21/c (No. 14). In their crystal structures, the basic building blocks are the B5O9 double rings, which are further linked by corner-sharing to form a two-dimension (2D) infinite corrugated ∞[B5O9]3− layer. However, since the 2D ∞[B5O9]3− layers possess the different arrangement in NaBaB5O9 and KBaB5O9, they are not isostructural. In addition, the UV–Vis–IR diffuse reflectance spectra exhibit that they have the relatively wide band gaps, 4.78 eV for NaBaB5O9 and 3.65 eV for KBaB5O9. The DSC analysis suggests that NaBaB5O9 melts congruently. And the first-principle theoretical studies are also carried out to aid the understanding of electronic structures and linear optical properties.

Two similarly stoichiometric mixed borates, NaBaB5O9 and KBaB5O9 have been synthesized, and their structures were determined by single crystal X-ray diffraction for the first time. Detailed structural analyses show that although NaBaB5O9 and KBaB5O9 possess the same stoichiometry and similar ∞[B5O9]3− layers, they are not isostructural owing to the different stocking direction of the ∞[B5O9]3− layers.Figure optionsDownload as PowerPoint slide