Rare‐Earth Substitution Induced Symmetry Breaking for The First Sc‐Based Nonlinear Optical Chalcogenide with High‐Performance

Abstract Chalcogenides are the most important infrared nonlinear optical (NLO) material candidates, and the exploration of high‐performance ones is attractive and challengeable. Hitherto, there is no NLO scandium (Sc) chalcogenides experimentally studied. Here, new quaternary Sc thiophosphate CsScP 2 S 7 (CSPS) was synthesized by the facile metal oxide‐boron‐sulfur/reactive flux hybrid solid‐state method. It crystallizes in the monoclinic chiral space group C 2, and the layered structure is composed by the new ScP 2 S 11 functional motifs built by ScS 6 octahedra and P 2 S 7 dimers, and the structure‐performance analysis reveals that the hyperpolarizability of ScP 2 S 11 is much greater than the assembled units (ScS 6 and PS 4 ), which makes the first NLO Sc chalcogenide CSPS exhibits strong NLO response (0.8 × AGS) and high laser‐induced damage threshold (LIDT) (4.3 × AGS), and a wide bandgap of 3.10 eV. With the coordination number's reduction of rare‐earth (RE) ion and the rearrangement of P 2 S 7 dimers, the centrosymmetric structure of CsREP 2 S 7 family can be broken via substitution with the smallest RE element Sc to form the noncentrosymmetric structure. This work not only discovers a new high‐performance infrared NLO material, but also will inspire researchers to explore more potential NLO Sc chalcogenides.