Results of thermal investigations of the amorphous five-component chalcogenide system Ge20As14(SexS1−x)52I14 are presented. Differential thermal analysis (DTA), derivative differential thermal analysis (DDTA), and dilatometry were
employed to determine the temperatures of softening and partial crystallization of the samples. Thermal treatment of the samples
at 1000°C and recording of the corresponding thermogravimetric (TG) and derivative thermogravimetric (DTG) curves allowed
an elucidation of the full mechanism of their decomposition, which proceeds via seven characteristic phase transitions.