SbO(OH)₂(IO₃): The First Polar Sb⁵⁺-Iodate with a Strong Second-Harmonic Generation Response and a Wide Bandgap

Widening the bandgaps while maintaining a strong second harmonic generation response has always been a research hotspot in the field of nonlinear optical iodate materials. A strategy involving covalent bonding is proposed that leverages the high valent later main group cation to construct iodates with predominantly covalent interactions. By using BiO(IO₃) as a template, the first Sb⁵⁺-containing polar iodate, SbO(OH)₂(IO₃) is successfully isolated. The introduction of the two hydroxide anions led to the reduction of layered BiO(IO₃) into 1D SbO(OH)₂(IO₃) in which two corner-sharing SbO₄(OH)₂ octahedra are further bridged by an iodate group. The covalently bonded [SbO(OH)₂]⁺ chains and the optimal packing fashion of the asymmetric IO₃ ^- groups generate a very strong second harmonic generation signal of 14 times that of KH₂PO₄. Furthermore, SbO(OH)₂(IO₃) exhibits a wide bandgap of 4.14 eV and a high laser induced damage threshold [27.9 × AgGaS₂, 0.2 × KH₂PO₄ (10 ns, 10 Hz)].