A new ultraviolet-transparent molybdate featuring a layered structure and moderate birefringence

Abstract

Birefringent materials exhibiting high optical anisotropy have garnered significant research interest due to their substantial scientific and technological importance in modern optoelectronics, particularly for their ability to manipulate light polarization. In this study, a barium molybdate compound with a two-dimensional layered structure, BaMo₅O₁₆, has been discovered through systematic exploration of the BaO–MoO₃ binary system. It crystallizes in the monoclinic space group C2/c and features [Mo₃O₁₃]_∞ layers composed of [MoO₅] and [MoO₆] polyhedra, with Ba²⁺ cations serving as interstitial ions. The compound has been characterized using infrared (IR) spectroscopy and ultraviolet-visible-near-infrared (UV-Vis-NIR) diffuse reflectance spectroscopy. First-principles calculations indicate that BaMo₅O₁₆ exhibits a birefringence value of Δn = 0.1@1064 nm.