The Rubidium Barium Borate Resulting from B7O15 Fundamental Building Block Exhibits DUV Cutoff Edge

The first rubidium barium borate, RbBaB7O12, has been prepared. Through analysis of single crystal structures, RbBaB7O12 is built from a three-dimensional [B7O12]∞ framework with two types of channels which are occupied by Rb+ and Ba2+ ions. The connection style of the fundamental building block (FBB) B7O15 is different from that of B–O FBBs existing in the other borates, which can be determined as the unprecedented unit. The structural performance relationship can be better understood by combining first-principles calculations and experimental results. For the RbBaB7O12, the indirect energy gap is 5.96 eV, which matches the experimental data (wavelength absorption < 190 nm). IR spectroscopy and thermal analysis have also been characterized. What's more, for all the available anhydrous hepta-borates, the structure comparisons about FBBs were carried out.