Abstract
Phase transitions in layer-type monoalkyl ammonium hexachlorostannate crystals (CnH2n+1NH3)2SnCl6 (abbreviated as CnSn) with n = 3,4,5,6,7 and 8 have been studied using the measurements of birefringence and thermal dilatation. The room temperature structure and temperature dependence of elastic moduli around the phase transition were determined for C4Sn.