Jerzy F Janik
The mechanochemical synthesis dwells on reactions induced in substrate mixtures under high energy ball milling conditions such as up to 900-1000 rpm speeds of planetary ball mills and use of extremely hard grinding balls. Starting from suitable mixtures of all four elements, we have successfully explored such a process for the preparation of nano powders of semiconducting kesterite Cu2 ZnSnS4 – prospective material for photovoltaics. Herein, described is a modification of the process in which, first, the Cu, Zn, and Sn metal powders are wet milled at 900 rpm forming the well mixed copper binary nanocrystalline alloys, i.e., Cu/Sn (1:1) and Cu/Zn (5:8). Stoichiometric amount of natural sulfur S is then included, and response processing is proceeded for a predetermined timeframe to bring about one clean quaternary item that is likely called a pre-kesterite. It is a cubic polytype with normal crystallite sizes of 8-12 nm (XRD), attractive (EPR), shows no 65Cu and 119Sn MAS NMR spectra, and needs semiconducting properties (UV-vis), albeit artificially and basically is like the semiconducting tetragonal kesterite.
