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NaCa5BO3(SiO4)2 with Interesting Isolated [BO3] and [SiO4] Units in Alkali- and Alkaline-Earth-Metal Borosilicates

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journal contribution
posted on 04.03.2019, 20:15 by Zhaohong Miao, Yun Yang, Zhonglei Wei, Zhihua Yang, Sujuan Yu, Shilie Pan
A new borosilicate, NaCa5BO3(SiO4)2, has been synthesized by a high-temperature solution method, which crystallizes in the centrosymmetric monoclinic space group P21/c (No. 14), having a tangled three-dimensional (3D) network including isolated [BO3] triangles, isolated [SiO4] tetrahedra, and [CaOn] (n = 7–9) and [NaO7] polyhedra. According to our surveys, it is the first compound containing both isolated [BO3] triangles and isolated [SiO4] tetrahedra in alkali- and alkaline-earth-metal borosilicates, which enriches the structure chemistry of borosilicates. The UV–vis–NIR diffuse reflectance spectrum shows that NaCa5BO3(SiO4)2 exhibits a wide transparent region which covers the near-IR, visible, and UV windows and displays a short UV cutoff edge at about 240 nm. Additionally, the thermal behavior (TG and DSC) and IR spectrum were also analyzed. For a deeper understanding of the relationships between the structure and properties, an analysis of theoretical calculations by density functional theory was also performed.