THERMAL-EXPANSION AND HIGH-TEMPERATURE TRANSFORMATION OF SNS AND SNSE

The thermal expansion of SnS and SnSe has been studied above room temperature up to the melting point of 1163 ± 5 K and 1135 ± 5 K, 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 with a ≈ c > b is observed at 878 ± 5 K and 807 ± 5 K, respectively. The lattice parameters of the high temperature modifications are for SnS a,c = 4.162 ± 0.006 A, b= 11.517 ± 0.015 A at 932K and for SnSe a,c = 4.313 ± 0.006A, b= 11.703 ± 0.015 A at 820 K. Both compounds maintain this structure type up to the melting points. © by Akademische Verlagsgesellschaft 1979