Crystal Growth, Structure, and Properties of a Non-Centrosymmetric Fluoride Borate, Ba3Sr4(BO3)(3)F-5

A non-centrosymmetric fluoride borate, Ba3Sr4(BO3)(3)F-5, 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 P6(3)mc (No. 186) and the following cell parameters: a = b = 10.8953(16) angstrom, c = 6.9381(15) angstrom, and Z = 2. It exhibits an intricate 3-dimensional framework of interconnecting Ba(1)O(1)(3)O(2)(4)F(2) polyhedra, Sr(1)O(2)(4)F(1)(2)F(3) polyhedra, Sr(2)O(2)(6)F(1)(3)F(3) polyhedra, and isolated BO3 triangles. The infrared spectrum indicates that the Ba3Sr4(BO3)(3)F-5 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 degrees C.