Reduction in lattice thermal conductivity of InSb by formation of the ZnIn 18GeSb 20 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 0.18 eV. However, a high ZT value has not been achieved in InSb because of its high lattice thermal conductivity (κ lat). In order to reduce the κ lat of InSb, In 3+ ions in InSb were partly replaced by Zn 2+ and Ge 4+ ions to form the ZnIn 18GeSb 20 alloy. Polycrystalline samples of ZnIn 18GeSb 20 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 723 K. The lat values of the quenched and slow-cooled samples at room temperature were 2.70 and 2.83Wm -1K -1, 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 multi-component system. The present study confirmed that the relatively large secondary phase would played an important role for the decreased the thermal conductivity in the Zn-In-Ge-Sb system unlike the AgPb mSbTe m+2 (LAST-m) system, in which nano-sized Ag-Sb inclusion are embedded in the PbTe matrix. © 2012 The Japan Institute of Metals.