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

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 CsScPS (CSPS) was synthesized by the facile metal oxide-boron-sulfur/reactive flux hybrid solid-state method. It crystallizes in the monoclinic chiral space group C2, and the layered structure is composed by the new ScPS functional motifs built by ScS octahedra and PS dimers, and the structure-performance analysis reveals that the hyperpolarizability of ScPS is much greater than the assembled units (ScS and PS), 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 PS dimers, the centrosymmetric structure of CsREPS 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.