Su Hongkang, Jiao Jiahao, Wang Shibin, An Donghai, Zhang Min
Research Center for Crystal Materials, CAS Key Laboratory of Functional Materials and Devices for Special Environments, Xinjiang Technical Institute of Physics & Chemistry, CAS, 40-1 South Beijing Road, Urumqi 830011, China.
Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
Dalton Trans. 2024 Jan 16;53(3):932-937. doi: 10.1039/d3dt03288d.
Borates are favored by materials scientists and chemists because of the significant electronegativity difference between B and O atoms and their flexible assembly modes resulting in abundant structures and excellent properties. For the design of deep-ultraviolet (DUV) optical crystals with excellent macroscopic performance, it is crucial to choose appropriate cations and anionic groups and microscopically reasonable assembly patterns. Herein, by introducing covalent tetrahedra ([MO], M = Mg, Al), two new mixed alkali metal and alkaline earth metal borates, RbMgBO and LiBaAl(BO), were synthesized using the melt method and high-temperature solution method. They contain M-B-O two-dimensional (2D) layers (2∞[MgBO] and 2∞[Al(BO)], respectively) composed of isolated B-O groups ([BO] and [BO], respectively) and metal-centered tetrahedral connectors ([MgO] and [AlO], respectively). Combining experiments and theoretical calculations shows that the two compounds have short cutoff edges (<200 nm) and moderate birefringences. Further analysis manifests that the isolated [MO] covalent tetrahedra can optimize the arrangement of anion groups, guarantee the balanced optical properties of materials, and point out the direction for further exploration of novel borate structures.
硼酸盐受到材料科学家和化学家的青睐，这是因为硼（B）原子和氧（O）原子之间存在显著的电负性差异，以及它们灵活的组装模式，从而产生了丰富的结构和优异的性能。对于设计具有优异宏观性能的深紫外（DUV）光学晶体而言，选择合适的阳离子和阴离子基团以及微观上合理的组装模式至关重要。在此，通过引入共价四面体（[MO]，M = Mg、Al），采用熔融法和高温溶液法合成了两种新型的混合碱金属和碱土金属硼酸盐，RbMgBO 和 LiBaAl(BO)。它们包含由孤立的 B - O 基团（分别为[BO]和[BO]）和以金属为中心的四面体连接体（分别为[MgO]和[AlO]）组成的 M - B - O 二维（2D）层（分别为 2∞[MgBO]和 2∞[Al(BO)]）。结合实验和理论计算表明，这两种化合物具有短截止边（<200 nm）和适度的双折射。进一步分析表明，孤立的[MO]共价四面体可以优化阴离子基团的排列，保证材料光学性能的平衡，并为进一步探索新型硼酸盐结构指明方向。
