Bi(IO₃)F₂: The First Metal Iodate Fluoride with a Very Strong Second Harmonic Generation Effect

The first metal iodate fluoride, Bi(IO₃ )F₂ , with a strong second harmonic generation (SHG) effect has been prepared. Bi(IO₃ )F₂ crystallizes in the polar space group C2 and features a three-dimensional [BiF₂ ]⁺ cationic framework with IO₃ groups capping the inner walls of the one-dimensional tunnels. This [BiF₂ ]⁺ cationic framework acts as a template for the assembly of the polar IO₃ units in a favorable superposed fashion, which leads to the polar structure of the material. Bi(IO₃ )F₂ displays a rather wide transmittance window (0.3-11 μm) and exhibits a very strong SHG response that is about 11.5 times larger than that of KH₂ PO₄ (KDP) under 1064 nm laser radiation and the same as that of KTiOPO₄ (KTP) under 2.05 μm laser radiation. Preliminary investigations indicate that Bi(IO₃ )F₂ is a promising nonlinear optical material in the visible and mid-IR region.