ZnIO3F: Zinc Iodate Fluoride with Large Birefringence and Wide Band Gap.

The first zinc iodate fluoride, ZnIO3F, was synthesized by the Zn2+ cation, the IO3 group, and fluorine ion, where Zn2+ is coordinated by O atoms from iodate and F atoms to form the ZnO4F2 polyhedron. It has outstanding optical characteristics, including large birefringence (Δ = 0.219 at 546 nm), wide band gap (Eg = 4.2 eV), and good thermal stability (over 475 °C), showing a subtle balance between the wide band gap and birefringence.