Structure of amorphous and glassy Sb2S3 and its connection with the structure of As2X3 arsenic chalcogenide glasses

Abstract Two types of amorphous and glassy Sb 2 S 3 were studied: amorphous orange-red powder obtained by precipitating a SbCl 3 solution using a stream of hydrogen sulphide in a bath of boiling water and a glassy material in the form of thin platelets obtained by the method of rotating cylinders. It was found by DTA that there is a great difference in the crystallization entropy and temperature between the powder and glass. Radial electron density distribution curves were measured for both modifications and a difference analysis showed that they can be considered to be much the same. From the distribution curves it follows that the basic unit is a trigonal SbS 3 pyramid which forms in the case of Sb 2 S 3 glass, a covalent random network while for the amorphous powder a random ordering of crystalline-like and band-like (Sb 2 S 3 ) n molecules can be considered as an appropriate model. A comparison of radial electron density distribution curves for As 2 X ( X =S, Se, Te and Sb 2 S 3 shows that Sb 2 S 3 belongs to the class of glassy As 2 X 3 structures. A rule is found that in this class of glasses the mutual ratios of diameters of corresponding coordination spheres are constant. On the basis of coordination numbers and of broadening functions for individual coordination spheres it is shown that in the series As 2 S 3 :As 2 Se 3 As 2 Te 3 a gradual transition from a layer-like to a random network takes place and that glassy Sb 2 S 3 can be put beside As 2 Te 3 . This process is a result of the difference between orpiment-like configurations and the As 2 X 5 ones, which evoke chain branching and interconnecting. This leads finally for As 2 Te 3 and Sb 2 S 3 to a random continuous covalent network. This process is confirmed by increase of both occupation numbers and the widths of broadening functions corresponding to individual coordination spheres.