Sr<sub>2</sub>[B<sub>5</sub>O<sub>8</sub>(OH)]<sub>2</sub> ⋅ [B(OH)<sub>3</sub>] ⋅ H<sub>2</sub>O: A Strontium Borate That Shows Deep‐Ultraviolet‐Transparent Nonlinear Optical Properties
Weifeng Chen, J. Lu, Jingjing Li, You‐Zhao Lan, Jian‐Wen Cheng, Guo‐Yu Yang
Abstract
Abstract A new noncentrosymmetric strontium borate, P 1‐Sr 2 [B 5 O 8 (OH)] 2 ⋅ [B(OH) 3 ] ⋅ H 2 O ( 1 ), has been synthesized under the hydrothermal condition. The P 1‐Sr 2 [B 5 O 8 (OH)] 2 ⋅ [B(OH) 3 ] ⋅ H 2 O shows a layered B−O network with 9‐ring windows in the ab plane. Sr 2+ cations, H 3 BO 3 , and H 2 O molecules are located in the voids of layers and interlayers, respectively. The P 1‐Sr 2 [B 5 O 8 (OH)] 2 ⋅ [B(OH) 3 ] ⋅ H 2 O is the first synthetic phase of veatchite, while the other three polymorphs are found in different natural minerals. This strontium borate is a potential deep‐ultraviolet‐transparent nonlinear‐optical (NLO) crystal whose second‐harmonic‐generation (SHG) intensity is 1.7 times that of KH 2 PO 4 (KDP) and is phase‐matchable. The short wavelength cutoff edge of compound 1 is below 190 nm. Density functional theory (DFT) calculations show that the B−O units are responsible for the nonlinear optical property.