Synthesis, Structure, and Characterization of Two Mixed-Cation Quaternary Chalcogenides KBaSnQ (Q = S, Se).

Two new isostructural metal chalcogenides, KBaSnS and KBaSnSe, have been isolated for the first time. They feature the intriguing ∞ 1[BaSnQ] (Q = S, Se) tunnel structures which are separated by K cations. Experiments combined with theoretical calculations demonstrate that KBaSnS possesses a large energy gap (3.09 eV), which is conducive for large laser-induced damage thresholds (LDTs), and maintains a relatively moderate SHG response (0.5 × AgGaS) in the meanwhile. Moreover, KBaSnS possesses good phase-matchability, which stems from its suitable birefringence (0.04@2.09 μm).