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.