The thermal expansion and high temperature transformation of SnS and SnSe*

Abstract

The thermal expansion of SnS and SnSe has been studied above room temperature up to the melting point of 1163 ± 5K and 1135 ± 5K, respectively, by X-ray diffraction techniques using a 190 mm Unicam high temperature camera. The changes of the lattice parameters indicate that the atomic positions in the (010) plane approach a square planar arrangement with increasing temperature. The transformation of SnS and SnSe from orthorhombic to a pseudotetragonal orthorhombic modification witha≈c<bis observed at 878 ± 5K and 807 ± 5K, respectively. The lattice parameters of the high temperature modifications are for SnS[unk]= 4.162 ± 0.006Å,b= 11.517 ± 0.015Å at 932 K and for SnSe[unk]= 4.313 ± 0.006Å,b= 11.703 ± 0.015Å at 820 K. Both compounds maintain this structure type up to the melting points.