Pb<sub>2</sub>TeV<sub>2</sub>O<sub>10</sub>: A Lead Vanadate Tellurate with Wide Mid-IR Transparency and Large Birefringence Induced by Multiple Birefringence-Active Groups
Yanyan Ding, Mengmeng Zhu, Junbo Wang, Bo Li, Hai-Xin Qi, Lili Liu, Yaoqing Chu
Abstract
Birefringent materials as the key materials in laser science and technology have attracted continuous attention due to their ability to modulate polarized light. Herein, a new lead vanadate tellurate, Pb 2 TeV 2 O 10, has been synthesized through the rational integration of different kinds of birefringence-active functional units. Pb 2 TeV 2 O 10 features a unique two-dimensional (2D) [TeV 2 O 10 ] ∞ layered structure consisting of [VO 6 ] 7– and [TeO 6 ] 6– octahedra, and Pb 2+ cations reside between the [TeV 2 O 10 ] ∞ layers. In addition, the rare edge-sharing mode of [VO 6 ] 7– and [TeO 6 ] 6– octahedra was found in this structure. Attributed to the high polarizability and appropriate arrangement of PbO 8, VO 6, and TeO 6 units, Pb 2 TeV 2 O 10 possesses a great theoretical birefringence of 0.275 at 532 nm, which is the largest among the vanadate tellurate family. The spectral tests also prove that Pb 2 TeV 2 O 10 showcases a broad transparency window (439 nm–10 μm), covering an important mid-infrared (IR) atmospheric window (3–5 μm). In addition, in order to improve the transparency, alkali and alkaline earth metal cations were introduced by the substitution strategy, and then the compound K 2 Sr 2 Te 2 O 9 was synthesized. It owns a shorter ultraviolet (UV) cutoff edge of 234 nm and a wider transparency window (234 nm–13.8 μm). The findings of Pb 2 TeV 2 O 10 and K 2 Sr 2 Te 2 O 9 enrich the structure chemistry of the tellurate family and provide new insights for designing new compounds with large optical anisotropy and wide spectral transparency.