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

Abstract A novel niobium oxyiodate sulfate, Nb 2 O 3 (IO 3 ) 2 (SO 4 ), 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. Nb 2 O 3 (IO 3 ) 2 (SO 4 ) 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×AgGaS 2 ). 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 H 2 SO 4 . Furthermore, Nb 2 O 3 (IO 3 ) 2 (SO 4 ) is a unique nonlinear optical (NLO) material among iodates and sulfates, because its SHG effect is mainly caused by the MO 6 units rather than the IO 3 or SO 4 units, which is demonstrated by density functional theory (DFT) calculations.