UV-Transparent SHG Material Explored in an Alkali Metal Sulfate Selenite System
Xinwei Zhang, Zhixiang Wang, Chun‐Li Hu, Yafeng Li, Jiang‐Gao Mao, Fang Kong
Abstract
The first examples of alkali metal selenite sulfates, namely, Na 8 (SeO 3 )(SO 4 ) 3 (1), Na 2 (H 2 SeO 3 )(SO 4 ) (2), and K 4 (H 2 SeO 3 )(HSO 4 ) 2 (SO 4 ) (3), were successfully synthesized by hydrothermal reactions. Their structures display three different zero-dimensional configurations composed of isolated sulfate tetrahedra and selenite groups separated by alkali metals. Na 8 (SeO 3 )(SO 4 ) 3 (1) features a noncentrosymmetric structure, while Na 2 (H 2 SeO 3 )(SO 4 ) (2) and K 4 (H 2 SeO 3 )(HSO 4 ) 2 (SO 4 ) (3) are centrosymmetric. Powder second-harmonic-generation measurements revealed that Na 8 (SeO 3 )(SO 4 ) 3 (1) shows a phase-matchable SHG intensity about 1.2 times that of KDP. UV–vis–NIR diffuse reflectance spectroscopic analysis indicated that Na 8 (SeO 3 )(SO 4 ) 3 (1) has a short UV cutoff edge and a large optical band gap, which makes it a possible UV nonlinear optical material. Theoretical calculations revealed that the birefringence of Na 8 (SeO 3 )(SO 4 ) 3 (1) is 0.041 at 532 nm, which is suitable for phase-matching condition. This work provides a good experimental foundation for the exploration of new UV nonlinear crystals in an alkali metal selenite sulfate system.