Aliovalent-cation-substitution-induced structure transformation: a new path toward high-performance IR nonlinear optical materials

Non-centrosymmetric (NCS) structure is the precondition and foundation for the development of high-performance nonlinear optical (NLO) crystals. In this research, a quaternary NCS thioantimonate, K2Ag3Sb3S7, is designed through an aliovalent-cation-substitution-induced strategy based on the centrosymmetric (CS) parent compound K2Sb4S7 and successfully obtained through a facile surfactant-thermal technology. The unique crystal structure of K2Ag3Sb3S7 belongs to the orthorhombic space group Cmc2(1) (no. 36) and is made of charge-balanced K+ cations and two-dimensional (2D) anionic layers [Ag3Sb3S7](2-) constructed by the vertex-sharing of (infinity)[Ag3SbS5](4-) and (infinity)[SbS2](-) chains. Remarkably, K2Ag3Sb3S7 not only possesses a phase-matching (PM) ability in the IR region, but also displays a perfect balance between a high second-harmonic-generation (SHG) coefficient (1.5 x commercial AgGaS2) and a large laser-induced damage threshold (3.2 x commercial AgGaS2). Moreover, theoretical studies uncover that the synergistic effects of three types of asymmetric building motifs (i.e., [SbS3], [Sb2S5] and [Ag3S6]) contribute to the large SHG effect and birefringence (Delta n). This study not only demonstrates that aliovalent cation substitution can be a robust means of obtaining the NCS thioantimonates but also provides a deeper insight into the structure-property relationship of IR-NLO chalcogenides.

Automated summary

In this study, a quaternary non-centrosymmetric thioantimonate was designed and successfully synthesized through an aliovalent-cation-substitution-induced strategy. The compound exhibits a unique crystal structure and excellent optical properties, showing phase-matching ability in the infrared region. The research reveals the synergistic effects of different building motifs on the optical effects.