Thermoelectric Properties of an Al-Doped In-Sn-Te-Based Alloy

In-Sn-Te-based alloys usually have low electrical and thermal conductivity. In the present work we substituted Al for In in an In-Sn-Te alloy and prepared an (In1.9Al0.1Te3)(0.08)(SnTe)(0.92) alloy by spark plasma sintering. Substitution of Al for In favors the formation of indium impurity levels in this structure and accounts for the decrease of the band gap (E (g)) and much of the increase of mobility and electrical conductivity. The thermal conductivity decreases from 1.72 W K-1 m(-1) to 1.44 W K-1 m(-1) with temperature, while that of the (In2Te3)(0.08)(SnTe)(0.92) alloy increases from 2.29 W K-1 m(-1) to 3.50 W K-1 m(-1). The thermoelectric figure of merit (ZT) of the sample increases with measurement temperature, and the highest ZT value of 0.28 was obtained at 668 K, being a factor of 4.5 greater than the maximum ZT value for the Al-free (In2Te3)(0.08)(SnTe)(0.92) alloy at 510 K.