Synthesis, structure, and nonlinear optical property of Bi0.33Sb0.67SI

Abstract The phase transition of SbSI from non-centrosymmetry to centrosymmetry occurs at 292K, which is too low for its practical applications such as ferroelectricity and nonlinear optics. Here, the substitution of Sb by Bi atoms is proposed to improve its phase transition temperature. A new chalcohalide, Bi0.33Sb0.67SI, has been successfully synthesized by self-flux method. It crystallizes in the non-centrosymmetric space group Pmc21 (No. 26) with a ​= ​4.1190 (9) A, b ​= ​10.225 (2) A, c ​= ​8.5318 (18) A. Different from the crystal structure of SbSI, Bi0.33Sb0.67SI is composed of two kinds of edge-sharing distorted square pyramid [MS3I2]5- (M ​= ​Bi or Sb), which form [ ∞ 1 M2S4I2]4- chains along a axis. The compound exhibits a moderate powder second harmonic generation signal at 2.09 ​μm, which was consistent with its non-centrosymmetric structure.