Structural Transformation and Second-Harmonic-Generation Activity in Rare-Earth and d<sup>0</sup> Transition-Metal Oxysulfides RE<sub>3</sub>NbS<sub>3</sub>O<sub>4</sub> (RE = Ce, Sm, Gd, Dy)
Xin Lian, Zhen‐Tao Lu, Wen‐Dong Yao, Sihan Yang, Wenlong Liu, Ru‐Ling Tang, Sheng‐Ping Guo
Abstract
Investigations of inorganic compounds with mixed anions have drawn much attention. Here, three oxysulfides, Sm3NbS3O4 (1), Gd3NbS3O4 (2), and Dy3NbS3O4 (3), are obtained by solid-state reactions. 1 and 2 crystallize in the polar space group Pna21, while 3 crystallizes in the centric space group Pnma. The anionic frameworks of 1 and 2 are built by isolated distorted [NbS2O4]7– octahedra, while [NbS3O4]9– is used for 3. 1 and 2 exhibit phase-matchable second-harmonic-generation (SHG) effects of about 0.3 and 0.4 × AGS at 2.1 μm. The [NbS2O4]7– octahedron was first used as a SHG-active motif for nonlinear-optical (NLO) materials. A systematic analysis of the transformation between these crystal structures, NLO performances, and magnetic behaviors, as well as first-principles theoretical studies, is presented. This work enriches the study on relatively rarely explored NLO-active metal oxysulfides.