Reduction in Lattice Thermal Conductivity of InSb by Formation of the ZnIn<sub>18</sub>GeSb<sub>20</sub> Alloy

Abstract

InSb is known to be a good candidate as a thermoelectric (TE) material owing to its high carrier mobility and narrow band gap of around 0.18eV. However, a high ZT value has not been achieved in InSb because of its high lattice thermal conductivity (¬lat). In order to reduce the ¬lat of InSb, In 3+ ions in InSb were partly replaced by Zn 2+ and Ge 4+ ions to form the ZnIn18GeSb20 alloy. Polycrystalline samples of ZnIn18GeSb20 were prepared by a powder metallurgy process combining mechanical alloying and hot pressing followed by water quenching or slow cooling. The TE properties of the quenched and slow-cooled samples were examined over the temperature range of room temperature to 723K. The ¬lat values of the quenched and slow-cooled samples at room temperature were 2.70 and 2.83Wm ¹1 K ¹1 , respectively. These values were approximately 6 times lower than that of InSb, presumably due to grain refinement through MA and effective alloy scattering from the multicomponent system. The present study confirmed that the relatively large secondary phase would played an important role for the decreased the thermal conductivity in the Zn­In­Ge­Sb system unlike the AgPbmSbTem+2 (LAST-m) system, in which nano-sized Ag­Sb inclusion are embedded in the PbTe matrix. [doi:10.2320/matertrans.M2012176]