SrMBe₂(BO₃)₂F₂ (M=Zn, Mg): Two SBBO-like Compounds Obtained by Cation Regulation

Cation regulation is a compelling strategy for developing new compounds with optimized crystal structure by atomic-scale manipulation. Herein, we report two new SBBO-like fluoroberyllium borates, SrMgBe₂(BO₃)₂F₂ (SMBBF) and SrZnBe₂(BO₃)₂F₂ (SZBBF). They crystallize in a trigonal system and feature a [Be₃B₃O₆F₃]∞ single layer stabilized by the incorporation of Mg²⁺/Zn²⁺ cations and F⁻ cations. Both compounds exhibit deep-UV absorption edges below 200 nm. Theoretical calculations confirm their potential as deep-UV birefringent materials, with correspinding birefringence values of 0.064 (SMBBF) and 0.063 (SZBBF) at 589 nm, respectively. This work demonstrates the effectiveness of cation regulation in designing novel borate-based optical materials.