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A2: Medium temperature materials

Thermoelectric performance of quaternary (PbTe)(1-x-y)(PbSe)x(PbS)y compounds

Sima Aminorroaya1, Heng wang2, Zachary Gibbs2, Yanzhong Pei2, David Mitchell1, Shi Xue Dou1, G Jeffrey Snyder2
1) Australian Institute for Innovative Materials (AIIM), Innovation Campus, University of Wollongong, NSW 2519, Australia2) Materials Science, California Institute of Technology, Pasadena, CA 91125, USA

Lead chalcogenides (PbQ, Q = Te, Se, S) have proved to possess high thermoelectric efficiency for both n-type and p-type compounds. Recently a significant improvement in thermoelectric performance of p-type ternary PbTe-PbSe and PbTe-PbS systems has been realized through alternating the electronic band structure and introducing nano-scale precipitates to bulk materials respectively. However, the quaternary system of PbTe-PbSe-PbS has received less attention.

We have shown that the thermoelectric efficiency of single phase p-type quaternary PbTe-PbSe-PbS is superior to ternary PbTe-PbSe and PbTe-PbS at similar carrier concentrations and the binary PbTe, PbSe and PbS alloys. The quaternary system shows a larger Seebeck coefficient than the ternary PbTe-PbSe alloy, indicative of a wider band gap, valence bands energy offset and heavier carriers effective mass. Surprisingly, the thermal conductivity of PbS-alloyed single phase alloys, originated from phonon scattering on high contrast atomic mass solute atoms, are as low as the thermal conductivity of nanostructured compounds. Therefore, the thermoelectric efficiency of nanostructured p-type quaternary lead chalcogenides were found to be lower than that of single phase alloys due to larger electrical resistivity.