Pb₂TeV₂O₁₀: A Lead Vanadate Tellurate with Wide Mid-IR Transparency and Large Birefringence Induced by Multiple...

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, Pb₂TeV₂O₁₀, has been synthesized through the rational integration of different kinds of birefringence-active functional units. Pb₂TeV₂O₁₀ features a unique two-dimensional (2D) [TeV₂O₁₀]_∞ layered structure consisting of [VO₆]^7- and [TeO₆]^6- octahedra, and Pb²⁺ cations reside between the [TeV₂O₁₀]_∞ layers. In addition, the rare edge-sharing mode of [VO₆]^7- and [TeO₆]^6- octahedra was found in this structure. Attributed to the high polarizability and appropriate arrangement of PbO₈, VO₆, and TeO₆ units, Pb₂TeV₂O₁₀ 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 Pb₂TeV₂O₁₀ 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 K₂Sr₂Te₂O₉ 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 Pb₂TeV₂O₁₀ and K₂Sr₂Te₂O₉ enrich the structure chemistry of the tellurate family and provide new insights for designing new compounds with large optical anisotropy and wide spectral transparency.