SnGa2GeSe6, a benign addition to the AM III2MIVQ6 family: synthesis, crystal structure and nonlinear optical performance

Abstract

A new selenide, SnGa₂GeSe₆, in the AM^III₂M^IVQ₆ family was synthesized for the first time by a high-temperature solid-state reaction. It crystallized in the non-centrosymmetric space group Fdd2 with cell dimensions of a = 47.195(9) Å, b = 7.5213(15) Å, c = 12.183(2) Å, and Z = 16. SnGa₂GeSe₆'s crystal structure is characterized by a crisscross network of two types of infinite chains (i.e. the ¹_∞[GaSe₃] chain and the ¹_∞[M₃Se₇] chain, where M represents the two metal sites randomly occupied by Ga and Ge atoms in a 1 : 1 ratio), which is similar to SnGa₂GeS₆ and diverges strongly from its Ba analogue owing to the substitution of Ba with Sn atoms that contain stereochemically active lone pair electrons. Careful experimental research has revealed that SnGa₂GeSe₆ exhibits an optical band gap of 1.98 eV and incongruent melting behavior. Furthermore, the second harmonic generation (SHG) intensity of the SnGa₂GeSe₆ powder sample is about 1.7 × AgGaS₂ at a particle size of 150–200 μm with a 2 μm laser as the fundamental light.