Dilatometric studies on structural phase transitions in (NH₄)₂ SnBr₆ crystal

Abstract

Thermal expansion along several directions was measured in the temperature range including the two transition temperatures. The orientation of the domain walls in two lower temperature phases was examined with a polarizing microscope. The results, together with the experiments so far reported, suggest the possibility that the symmetry of the phase between -116°C and -129°C is trigonal, in contrast to being tetragonal as previously conjectured