Guanglian Sun, Xiaofang Qi, Hongping Wu, Zhanggui Hu, Jiyang Wang and Yicheng Wu
Inorg. Chem. Front., 2024,11, 3245-3253
DOI:
10.1039/D4QI00840E,
Research Article
Birefringence determined by optical anisotropy is one of the most pivotal and fundamental performance of optical materials. However, optimizing the birefringence remains a significant challenge. Herein, a simple and effective method of cation chemical substitution for improving the birefringence has been accomplished and three Y-based borates, namely, LiNa2Y(BO3)2, RbNa2Y(BO3)2 and RbSrY(BO3)2, were successfully synthesized. They all have deep-ultraviolet (DUV) cutoff edges below 190 nm. Single-crystal analysis reveals that LiNa2Y(BO3)2 and RbNa2Y(BO3)2 possess three-dimensional (3D) frameworks with small channels filled by alkali metal cations, whereas RbSrY(BO3)2 features a two-dimensional (2D) layered structure separated by alkali metal and alkali-earth metal cations. The birefringence exhibits a progressive doubling increase from LiNa2Y(BO3)2 (0.017@532 nm) to RbNa2Y(BO3)2 (0.033@532 nm) and then to RbSrY(BO3)2 (0.070@532 nm). Using cation size arguments, coordination environment, and the arrangement of groups demonstrate that cation substitution have a decisive effect on the birefringence enhancement. In addition, other optical and thermal properties of the three title compounds were characterized. The structure–property relationships were analyzed by the first-principles calculations.
