Role of the solvent medium in the wet-chemical synthesis of CuSbS 2 , Cu 3 SbS 3 , and bismuth substituted Cu 3 SbS 3
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J. Chem. Sci. (2020)132:132 https://doi.org/10.1007/s12039-020-01831-z
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Role of the solvent medium in the wet-chemical synthesis of CuSbS2, Cu3SbS3, and bismuth substituted Cu3SbS3 SHALU ATRI, MEENAKSHI GUSAIN, PRASHANT KUMAR, SITHARAMAN UMA and RAJAMANI NAGARAJAN* Materials Chemistry Group, Department of Chemistry, University of Delhi, Delhi 110 007, India E-mail: [email protected]; [email protected]; [email protected]; [email protected]; [email protected] MS received 14 February 2020; revised 13 July 2020; accepted 20 July 2020
Abstract. Co-thermal decompositions of equimolar concentrations of thiourea complexes ([Cu(tu)3]Cl and [Sb(tu)2]Cl3) in ethylene glycol and ethanolamine were attempted. Based on the results from powder X-ray diffraction, Raman spectroscopy, and energy dispersive spectral analysis of the products, Cu3SbS3 in cubic symmetry emerged from ethylene glycol. In contrast, orthorhombic CuSbS2 resulted from the ethanolamine medium. The generation of copper-rich and copper-poor sulfides was found to be the major reason behind the formation of these stoichiometries of the Cu-Sb-S system as verified by reacting the preformed Cu-S and Sb-S species in ethanolamine and ethylene glycol. Attempts to include bismuth (up to 50 mol%) for antimony were successful only in ethylene glycol medium. The inclusion of bismuth stabilized the orthorhombic form of Cu3SbS3, possibly due to the non-bonded lone pairs present on Bi3? and Sb3?-ions. The inclusion of bismuth confirmed from the successful refinement of powder X-ray diffraction pattern by the Rietveld method, Raman spectroscopy, and energy dispersive spectroscopy analysis. CuSbS2, Cu3SbS3 (cubic) and Cu3Sb0.50Bi0.50S3 showed broad absorption extending up to visible region in their UV-visible spectra. The bandgap values of 1.31, 1.40 and 0.94 eV were estimated by Tauc plots for Cu3SbS3, CuSbS2, and Cu3Sb0.50Bi0.50S3, respectively. Keywords. Powders; Chemical preparation; X-ray methods; Optical properties.
1. Introduction The recent trends in research are directed towards the development of renewable energy sources. There are specific efforts to recover industrial and automobile waste heat and convert them into electricity. The thermoelectric generators, capable of converting waste heat to power, consist of p-type and n-type semiconducting elements/compounds. Copper-based chalcogenides are promising semiconductor materials exhibiting applications in the energy sector as photovoltaic, thermoelectric, supercapacitor, dye-sensitized solar cells, and as electrodes in batteries.1–5 For sustainable solar cell materials, copper antimony/bismuth sulfides have superseded copper indium sulfide or copper gallium sulfide from many aspects, including cost-effective nature, non-toxicity, and earth
abundance. CuSbS2 (Chalcostibite), Cu12Sb4S13 (Tetrahedrite), Cu3SbS3 (Skinnerite), and Cu3SbS4 (Fematinite) are the four accessible ternary phases which are inherently
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