Effect of Cooling Conditions on the Microstructure and Thermoelectric Properties of Zn/Si-Codoped InSb

InSb is a good candidate thermoelectric (TE) material owing to its high carrier mobility and narrow band gap around 0.18 eV. However, a high figure of merit (ZT) value has not been achieved with InSb because of its high lattice thermal conductivity (kappa (lat)). To reduce the kappa (lat) of InSb, we prepared a ZnIn18SiSb20 alloy by Zn/Si codoping into the In lattice sites of InSb. Polycrystalline samples of ZnIn18SiSb20 were prepared by a solid-state reaction method combined with hot pressing. To investigate the microstructures and TE properties resulting from different cooling conditions, samples were prepared by water quenching or slow cooling after an annealing process. The different cooling conditions led to different ZnIn18SiSb20 microstructures and TE properties. The electrical transport properties showed that both samples exhibited metal-like behavior and p-type conduction. The thermal conductivity values of the quenched and slow-cooled samples at room temperature were 8.7 W m(-1) K-1 and 11.7 W m(-1) K-1, respectively. A maximum ZT value of 0.23 was obtained at 723 K for the quenched ZnIn18SiSb20 sample.