Synthesis, structures and properties of two new selenite optical materials: K2Zn3Se4O12 and K4Zn3V4Se2O19†

Two new selenites, K₂Zn₃Se₄O₁₂ (compound 1) and K₄Zn₃V₄Se₂O₁₉ (compound 2), have been successfully synthesized by solid-state reactions in vacuum tubes. Compound 1 consists of a three-dimensional (3D) framework with [SeO₃] triangular pyramids and [ZnO₄] tetrahedra in the monoclinic space group P2₁/c (No. 14). Compound 1′s cut-off edge is below 344 nm, based on its UV-Vis-NIR diffuse reflectance studies, and theoretical calculations indicate a birefringence of around 0.043 at 1064 nm. The two-dimensional layer of compound 2, in contrast, is made up of [SeO₃] triangular pyramids, [ZnO₄] tetrahedra, and [V₄O₁₃] tetrahedra. It crystallizes in the monoclinic space group C2/c (No. 15). Its UV-Vis-NIR diffuse reflectance studies demonstrate that the compound's cut-off edge is lower than 330 nm.