Ba3S[SnOS3] and [Ba2Sn]S[Ge2O7]: two antiperovskite oxychalcogenides with good IR nonlinear optical performances

Abstract

Infrared (IR) nonlinear optical (NLO) materials have important applications in various fields. However, the development of new IR NLO materials with improved performance remains a huge challenge due to distinct microstructural requirements between second-harmonic generation (SHG) and band gaps. Herein, two new non-centrosymmetric and polar antiperovskite-type X₃BA (A and B = anion or anionic group; X = cation) oxychalcogenides, Ba₃S[SnOS₃] and [Ba₂Sn]S[Ge₂O₇], were successfully designed and synthesized by chemical substitution. In the structures, the three-dimensional framework is formed by the corner-sharing connection of [SBa₆] and [SBa₄Sn₂] octahedra, respectively. Furthermore, the [SnOS₃] groups and [Ge₂O₇] dimers occupy the framework interstices to form the antiperovskite structure. The theoretical calculations and optical property measurements indicate that the materials exhibit good optical properties, including wide band gaps (3.13–3.60 eV), strong SHG responses (0.8–2.0 × AgGaS₂(AGS)@2090 nm), high laser-induced damage thresholds (3–5 × AGS), and moderate birefringence (0.021–0.074@1064 nm). This work further highlights the potential of the antiperovskite structure for the development of high-performance IR NLO materials.