Structural and Optical Characterization of Mechanochemically Synthesized CuSbS₂†

The present work describes experimental studies related to the characterization of CuSbS₂ directly synthesized after 2 h of mechanochemical synthesis (MCS) at 340 rpm, starting from mixtures of elemental powders. X-ray diffraction (XRD) and UV-VIS-NIR spectroscopy were carried out to analyze the crystal structure, degree of crystallinity, crystallite size and optical properties of the mechanochemically synthesized CuSbS₂ powders. Rietveld refinement was carried out using Diffrac. TOPAS (Bruker AXS). Thermal stability of the synthesized materials was evaluated by the vacuum thermal heat treatment of the mechanochemically synthesized CuSbS₂ powders at 350 °C for 24 h. Furthermore, the CuSbS₂ powders were also analyzed by field-emission scanning electron microscopy (FE-SEM), laser diffraction, and differential thermal analysis.

As the Figure 1 shows, all XRD peaks were assigned to the orthorhombic chalcostibite phase with the space group Pnma (COD database file 9003580). This result is significant and demonstrates the direct synthesis of CuSbS₂ powders at room temperature after a short-duration MCS process. The absence of any phase transformation with heat treatment at 350 °C/24 h revealed the strong structural stability of the produced phase. The optical bandgap was determined to be around 1.41 eV, in good agreement with the values reported in the literature. This suggests that mechanochemically synthesized CuSbS₂ compounds can be considered suitable to be used as absorber materials of thin-film solar cells. Additionally, the obtained results also indicate that the MCS process is a viable and promising route for the preparation of materials for photovoltaic applications.