Thermoelectric properties of p-type Te-doped (Bi,Sb)2Te3 alloys by mechanical alloying and plasma activated sintering

In the present work, p-type (Bi,Sb)2Te3 alloys with excess Te addition were prepared by mechanical alloying and plasma activated sintering. A preferentially orientated microstructure with the basal planes (0 0 l) perpendicular to the pressing direction was formed, and the orientation factors of the (0 0 l) planes of the Bi0.5Sb1.5Te3 and Bi0.4Sb1.6Te3 alloys were 0.12 and 0.11, respectively. Effect of excess Te content on the thermoelectric properties of the (Bi,Sb)2Te3 alloys was investigated and the figure of merit of the Bi0.4Sb1.6Te3 alloys decreased from 5.26 × 10−3 to 4.44 × 10−3 K−1 with increasing the amount of excess Te to 8 wt.%, this should be ascribed to the fact that the chemical composition of the δ matrix phase displayed indifference with varying excess Te content and the presence of free Te second phase.