Recent advances in F-containing iodate nonlinear optical materials

Metal iodates containing I(V) with lone electron pairs in an asymmetric coordination geometry exhibit excellent second-harmonic generation (SHG) responses, wide transmission range and large band gaps. During the past ten years, metal iodates have been widely studied, and introducing large electronegative fluorine atoms into metal iodates has also attracted much attention. These F-containing iodates are different from pure iodates in terms of composition, symmetry and transmittance. Especially because oxide-fluoride heterolepic anion groups can exhibit interesting structure-directing properties, e.g. trans- and cis-directing properties, these F-containing iodates also have better structure designability. Therefore, in this review, we will review the research progress of F-containing iodates and address the effect of structure-directing properties of oxide-fluoride anions on the crystal structures of F-containing iodates. Since the valence of the central cations will greatly affect the distortions and configurations of the oxide-fluoride anion groups, these F-containing iodates will be classified and introduced according to the different valences of the central cations.