Na2ZnSn2S6: A mixed-metal thiostannate with large second-harmonic generation response activated by penta-tetrahedral [ZnSn4S14]10− clusters

Abstract

A sodium zinc thiostannate Na2ZnSn2S6 is reported with its interesting structural features and property characteristics. It crystallizes in the polar space group Fdd 2 (No. 43) with the unit cell parameters of a =12.945(3) A, b =23.556(5) A, c =7.2774(15) A and Z =8. In its structure, Zn-centered penta-tetrahedra [ZnSn4S15]12− clusters arrange regularly along the diagonals of ab and ac planes to form a 3D tunnel structure with charge-balanced Na+ cations located inside the tunnels. Note that SnS4 tetrahedra connect with each other by sharing corners to form infinite ∞ [SnS3] n chains that are rarely found in known alkali-thiostannates. Remarkably, Na2ZnSn2S6 exhibits the good NLO performances, such as large SHG response (4 times that of AgGaS2 at 55–88 μm under the 2.09 μm radiation), wide infrared (IR) transmission region (0.35–25 μm) and relatively high laser damage threshold (77.5 MW/cm2, ~2 times that of AgGaS2). Theoretical calculations have also been performed to investigate the structure-property relationship and the results indicate that the origin of NLO effect can be attributed to the penta-tetrahedra [ZnSn4S15]12− clusters.