The structure of amorphous Se–S prepared by mechanical alloying

Abstract

The structure of trigonal Se consists of chains and that of rhombic S is based on a packing of S 8 ring molecules. The mechanical alloying (MA) of Se–S powders, therefore, leads to a mixture of chains and ring molecules. In the X-ray diffraction pattern, the Bragg peaks associated with trigonal Se and rhombic S gradually disappear and a broad halo becomes dominant with increasing milling time. A longer milling time was required for transforming the crystalline to the amorphous state with increasing S content. Amorphization of the Se–S powders occurred in the range 0–40 at% S. The Se–Se first neighbour distance and coordination number, obtained from neutron diffraction measurements, decrease as the amorphization proceeds. The decrease in the first neighbour coordination number indicates a shortening of the Se chains.