Effects of Ga- and In-doping on the Thermoelectric Properties in Ba-Ge Clathrate Compounds

摘要

The crystal structures and thermoelectric properties of Ba-Ge type-I clathrate compounds (Ba_8GaxGe_(46-x) and Ba_8Ga_(16-Y)ln_YGe_(30)) have been investigated as a function of Ga and In contents.BasGaxGe46-x alloys have a crystal structure that contains an ordered arrangement of Ge vacancies,forming a superstructure based on the normal type-I structure until X reaches 3,whereas they have the normal type-I structure when X exceeds 3.The dimensionless thermoelectric figure of merit (ZT) increases with the increase in the Ga content,exhibiting the highest value of 0.49 for Ba_8Ga_(16)Ge_(30).The power factor for Ba_8Ga_(10)In_6Ge_30) is 1.5 times that for Ba_8Ga_(16)Ge_30) so that the In containing alloy exhibits a ZT value as high as 1.03 at 700 deg C.