Effect of a Sulfur Precursor on the Hydrothermal Synthesis of Cu₂MnSnS₄

Cu₂MnSnS₄ (CMTS) is acknowledged as an alternative to traditional semiconductors. The structure and microstructure of synthetic CMTS depend on, among other things, the types of sulfur sources used. Traditionally obtained CMTS mostly has a tetragonal structure. In this study, the effect of using thiourea (Tu) or Na₂S as a sulfur source on the product structure was compared using hydrothermal synthesis at 190 °C for 7 days (ethylene glycol with water in the presence of poly(vinylpyrollidone) was used as a solvent). When Tu was used, CMTS precipitated in the form of concentric microspheres, 1-1.5 µm in size, consisting of hexagonal (in the cores) and tetragonal (the rims) forms. Most probably, the rapidly formed hexagonal nucleus was later surrounded by a slower-forming rim with a tetragonal structure. In contrast, when Na₂S was used as a precursor, microspheres were not formed and a fine crystalline material with a homogeneous tetragonal structure was obtained. This allowed for the choice of micromorphology and product structure during synthesis.