Xueqing Liu, Xinyue Shi, Yuan Fang, Yipeng Pang, Degao Zhong, Bing Teng, Y Huang, Zhoubin Lin, Shijia Sun
Silicates are a highly attractive system for exploring ultraviolet (UV) optical crystals. However, silicates typically exhibit relatively small birefringence due to the weak polarizability anisotropy of tetrahedral units. 4d 0 transition-metal Zr 4+ not only helps to enhance structural anisotropy due to its second-order Jahn–Teller effect but also has relatively low electronegativity, and the binding of Zr to O with high electronegativity enhances the ionicity of Zr–O bonds, which helps reduce the UV cutoff edge. Herein, by introducing Zr 4+ into the silicate system, K 2 ZrSi 2 O 7 with enhanced birefringence and a short cutoff edge was successfully synthesized by a high-temperature solid-state method. It exhibits an enhanced birefringence of 0.047 @ 550 nm, which is at least twice that of most known UV optical silicates. Combined with its wide transmission range, short UV cutoff edge, and high thermal stability, K 2 ZrSi 2 O 7 has become a promising candidate for a UV birefringent material. This work is anticipated to provide useful guidance for exploring short-UV birefringent crystals with enhanced optical properties.