A Niobium Oxyiodate Sulfate with a Strong Second‐Harmonic‐Generation Response Built by Rational Multi‐Component Design

A novel niobium oxyiodate sulfate, Nb₂O₃(IO₃)₂ (SO₄), was fabricated by a rational multi‐component design under moderate hydrothermal conditions. This multi‐component design is inspired by an interesting niobium oxysulfate reaction, which opens a new door for synthetic method to effectively introduce refractory metals such as Nb into crystal structures by hydrothermal synthesis. Nb₂O₃(IO₃)₂(SO₄) features a cube‐like topological structure with a large phase‐matching second harmonic generation (SHG) response (6×KDP), a wide transparency window (0.38–8 μm), and a high laser damage threshold (LDT) (20×AgGaS₂). It has the highest thermostability (stable up to 580 °C under air) among reported non‐centrosymmetric (NCS) iodates and sulfates and is stable in water and even concentrated H₂SO₄. Furthermore, Nb₂O₃(IO₃)₂(SO₄) is a unique nonlinear optical (NLO) material among iodates and sulfates, because its SHG effect is mainly caused by the MO₆ units rather than the IO₃ or SO₄ units, which is demonstrated by density functional theory (DFT) calculations.     

LiMII(IO3)3 (MII=Zn and Cd): Two Promising Nonlinear Optical Crystals Derived from a Tunable Structure Model of α‐LiIO3

Excellent nonlinear optical materials simultaneously meet the requirements of large SHG response, phase‐matching capability, wide transparency windows, considerable energy band‐gap, good thermal stability and structure stability. Herein, two new promising nonlinear optical (NLO) crystals LiM^II(IO₃)₃ (M^II=Zn and Cd) are rationally designed by the aliovalent substitution strategy from the commercialized α‐LiIO₃ with the perfect parallel alignment of IO₃ groups. Compared with parent α‐LiIO₃ and related A^I₂M^IV(IO₃)₆, the title compounds exhibit more stable covalent 3D structure, and overcome the racemic twinning problem of A^I₂M^IV(IO₃)₆. More importantly, both compounds inherit NLO‐favorable structure merits of α‐LiIO₃ and show larger SHG response (≈14× and ≈12×KDP), shorter absorption edge (294 and 297 nm) with wider energy band‐gap (4.21 and 4.18 eV), good thermal stability (460 and 430 °C), phase‐matching behaviors, wider optical transparency window and good structure stability, achieving an excellent balance of NLO properties.