Metal iodates, as promising second-order nonlinear optical (NLO) materials, attract much attention. It has been reported that two-site alivolent substitution is an effective route for exploring novel NLO materials.

In a recent study published in Angew. Chem. Int. Ed., three-site alivolent substitution was proposed by Prof. MAO Jianggao's at Fujian Institute of Research on the Structure of Matter of Chinese Academy of Sciences as a facile route for new NLO materials.

Researchers obtained two new metal iodates, α- and β-Ba₂[GaF₄(IO₃)₂](IO₃) via replacing V⁵⁺ cation with Ga³⁺ cation, and in the meantime two O^2- anions being substituted by two F^- anions from the parent compounds α- and β-Ba₂[VO₂F₂(IO₃)₂](IO₃).

They found that α- and β-Ba₂[GaF₄(IO₃)₂](IO₃) maintain the overall topology with large polarizability, and the favorable alignment of [Ga(IO₃)₂F₄]^3- and IO₃^- anions results in a large SHG response (~ 6 × KDP).

Meanwhile, they showed that the introduction of post main group element Ga and strong electronegativity anion F^- generates the wide bandgap and high relevant LDTs (4.61 eV, 29.7 × AGS and 4.35 eV, 28.3 × AGS).

These results manifested that the obtained two new metal iodates could be the valuable-prospective NLO materials application in the region from ultraviolet to mid-infrared.

Different from the two-site alivolent substitution, three-site alivolent substitution features a displacement of d⁰-TM octahedron with non-d⁰-TM octahedron because of the charge difference of two for the cation. By this substitution, researchers can greatly expand the family of NLO materials.

Three-site alivolent substitution could be a facile and effective route for exploring new NLO materials.