LiBa3Al2B3O11: a deep-ultraviolet transparent optical borate featuring a 2D [Al2B3O11]∞ layered structure

Abstract

Borates have garnered significant attention due to their rich structural diversity and versatile applications, particularly in the ultraviolet (UV) and deep-ultraviolet (DUV) transparent optical regions. In this study, a new aluminum borate, LiBa₃Al₂B₃O₁₁, was successfully synthesized for the first time. Its structural framework consists of interconnected [BO₃]³⁻ triangles and [Al₂O₆]_∞ chains, with Ba and Li atoms occupying the interstitial sites. Within the a–c plane, the crystal features two-dimensional [Al₂B₃O₁₁]_∞ layers composed of 16-membered rings (Al₂B₂O₆), which remains a unique structure motif among aluminum borates. Experimental results confirmed a UV transmission cut-off edge below 200 nm, indicating its potential for applications in DUV optics.