CsHgNO<sub>3</sub>Cl<sub>2</sub>: A New Nitrate UV Birefringent Material Exhibiting an Optimized Layered Structure
Ying Long, Xuehua Dong, Ling Huang, Hongmei Zeng, Zhien Lin, Guohong Zou
Abstract
Developing effective strategies to design novel, excellent birefringent materials has become an emerging challenge. Herein, we report a new UV nitrate birefringent material, CsHgNO3Cl2, which is an analogue of the known UV carbonate nonlinear optical crystal KCaCO3F. In CsHgNO3Cl2, a perfect layered structure was produced owing to the alliance of a planar π-conjugated anion NO3– and highly electropolarized Hg2+ cation. The optimized layered structure that is beneficial in enlarging the optical anisotropy induced a large birefringence (Δn = 0.145@546 nm) for CsHgNO3Cl2, even superior to that of the well-known commercial birefringent material α-BBO in the UV region. The strategy that the optimization of planar functional group arrangement is able to boost birefringence is expected to guide the development of high-performance birefringent materials in the future, especially in the field of UV.