From NaScGaQ (Q = S, Se) to KGaInS: substitution of Sc with In to achieve doubled birefringence.

The exploration of novel compounds with new crystal and electronic structures is essential for advancing the development of functional materials. Here, three novel isomorphic quaternary alkali-metal chalcogenides, AMQ (A = Na, K; M = Sc, Ga and In; Q = S, Se), with a new structure type have been obtained by a facile reactive flux assisted boron-chalcogen solid-state method, and adopt a 3 {[MQ]} open-framework architecture with A ions occupying the cavities to balance charges. Subtle modulation of the M-Q bonds induces a twofold enhancement in optical birefringence (Δ), observed from NaScGaQ (Q = S, Δ = 0.

From Centrosymmetric EuGaS to Noncentrosymmetric EuMgGaS via Introduction of Distorted MgS Octahedron: Featuring Wide Bandgap and Nonlinear Optical Activity.

Rare-earth chalcogenides have emerged as promising materials for infrared nonlinear optical (IR NLO) applications owing to their exceptional physicochemical properties. In this work, the introduction of distorted [MgS] octahedra into the parent EuGaS induces a centrosymmetric to noncentrosymmetric structural transformation, leading to the successful synthesis of novel EuMgGaS (EMGS). Its structure is composed of [EuS] triangular prisms, [MgS] octahedra, and [GaS] tetrahedra, among which the [MgS] octahedra show the largest distortion degree.

A Series of Pentanary Rare-Earth Oxysulfides Obtained by Heterovalent Cation and Anion Cosubstitution Exhibiting Nonlinear Optical Activity and Ultrawide Band Gaps.

Considering the shortcomings of commercial infrared nonlinear optical (NLO) crystals, it is necessary and urgent to explore new ones. Oxychalcogenides are regarded as potential candidates due to their abundant structures and possible balance between NLO indicators. Herein, isostructural REGaGeOS (RE = La (), Ce (), Pr (), and Nd ()) were derived from KNbGeO () via the heterovalent cation/anion cosubstitution strategy.

From Orthorhombic CuGeS to Cubic CuHgGeS: Second-Harmonic Generation and Photocurrent Responses.

A new noncentrosymmetric sulfide, CuHgGeS (CHGS), has been successfully synthesized via a heterovalent substitution strategy based on argyrodite-type CuGeS (CGS). Benefiting from the substitution of Cu with Hg cation, the structure changes from orthorhombic 2 to cubic 23. CHGS exhibits obvious nonlinear optical (NLO) activity, while CGS not.