New Nonlinear Optical Crystal: NaBa4Al2B8O18Cl3

Single crystals of NaBa4Al2B8O18Cl3 have been grown with sizes up to 34 × 34 × 16 mm3 from the NaF–LiCl flux by the top-seeded solution growth method. The compound crystallizes in the tetragonal system, space group P42nm, with a = 12.0480 (16) Å, c = 6.8165 (11) Å, α = β = γ = 90°, and two formula units per cell. The NaBa4Al2B8O18Cl3 compound is built up of infinite anionic groups of [AlB4O12]9– formed by two BO4 tetrahedra, one AlO4 tetrahedra, and two BO3 triangles. Optical properties including ultraviolet transmission, IR spectrum, and second-harmonic generation of NaBa4Al2B8O18Cl3 crystals were reported. Refractive indices were measured by the minimum deviation technique and fitted to the Sellmeier equations. Thermal properties such as the DSC and thermal expansion were reported. The mechanical properties including the hardness, density, and chemical stability were also reported.

采用顶部籽晶溶液生长法（top-seeded solution growth method），以NaF–LiCl为助熔剂，成功生长出尺寸可达34×34×16 mm³的NaBa4Al2B8O18Cl3单晶。该化合物结晶于四方晶系，空间群为P42nm，晶胞参数为a=12.0480(16) Å、c=6.8165(11) Å，α=β=γ=90°，每个晶胞包含2个化学式单元。NaBa4Al2B8O18Cl3化合物由无限延伸的[AlB4O12]9–阴离子基团构成，该基团由2个BO4四面体、1个AlO4四面体以及2个BO3三角形配位单元组装而成。本文报道了NaBa4Al2B8O18Cl3晶体的光学性能，涵盖紫外透射性能、红外光谱以及二次谐波产生（second-harmonic generation）特性。采用最小偏向角法测试了其折射率，并将测试数据拟合至塞米尔（Sellmeier）方程。热性能方面，包括差示扫描量热（DSC）分析结果与热膨胀性能均已有相关报道。机械性能（涵盖硬度、密度与化学稳定性）同样已有研究报道。