Crystal Growth, Structure, and Properties of a Non-Centrosymmetric Fluoride Borate, Ba₃Sr₄(BO₃)₃F₅

A non-centrosymmetric fluoride borate, Ba3Sr4(BO3)3F5, has been synthesized by solid state reaction techniques, and a single crystal was grown by the top-seeded solution growth method using NaF as flux. Single-crystal X-ray diffraction analysis shows the structure to be hexagonal with space group P63mc (No. 186) and the following cell parameters: a = b = 10.8953(16) Å, c = 6.9381(15) Å, and Z = 2. It exhibits an intricate 3-dimensional framework of interconnecting Ba(1)O(1)3O(2)4F(2) polyhedra, Sr(1)O(2)4F(1)2F(3) polyhedra, Sr(2)O(2)6F(1)3F(3) polyhedra, and isolated BO3 triangles. The infrared spectrum indicates that the Ba3Sr4(BO3)3F5 crystal contains characteristic BO33− groups as its basic structural units, which is consistent with the crystallographic study. The transparency spectrum shows that the as-grown crystal is transparent in the wavelength range of 270 to 2550 nm, the highest transmittance exceeds 85%, and the UV cutoff wavelength is about 210 nm.The thermal analysis shows that it is chemically stable and melts congruently at 1174.3 °C.本研究通过固相反应法合成了一种非中心对称氟硼酸盐Ba3Sr4(BO3)3F5，并采用以氟化钠（NaF）为助熔剂的顶部籽晶溶液生长法制备了其单晶。经单晶X射线衍射分析，该晶体属六方晶系，空间群为P63mc（编号186），晶胞参数为：a = b = 10.8953(16) 埃，c = 6.9381(15) 埃，Z=2。该晶体呈现出由相互连接的Ba(1)O(1)3O(2)4F(2)多面体、Sr(1)O(2)4F(1)2F(3)多面体、Sr(2)O(2)6F(1)3F(3)多面体以及孤立的BO3三角形基团构成的复杂三维骨架结构。红外光谱测试表明，Ba3Sr4(BO3)3F5晶体以特征性BO3³⁻基团作为基本结构单元，这与晶体学分析结果一致。透光光谱测试显示，该生长态晶体在270~2550 nm波长范围内具有透光性，最高透过率超过85%，紫外截止波长约为210 nm。热分析结果表明，该化合物化学稳定性良好，在1174.3 ℃下发生一致熔融。