Effect of Sn Doping on the Thermoelectric Performance of the Complex p-Type Zr0.5Hf0.5Co0.3Ir0.7Sb1-ySny Half-Heusler System

Pierre Ferdinand P. Poudeu



2126 HH Dow

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Nathan J Takas, Michael R Shabetai, and Pierre FP Poudeu (2011)

Science of Advanced Materials, 3(4):571-576.

Half-Heusler (HH) alloys with the general composition Zr0.5Hf0.5Co0.3Ir0.7Sb1-ySny (y = 0.0-0.6) were synthesized via solid state reaction and their thermoelectric performance was investigated from 300-725 K. This system was designed from our earlier study of the thermoelectric performance of the complex HH system with general composition Zr0.5Hf0.5Co1-xIrxSb0.99Sn0.01, which displayed the highest figure of merit, ZT similar to 0.09 at 750 K for the composition with x = 0.7. The synthesized materials were characterized by PXRD and DSC. Single phases of the synthesized HH materials were obtained for compositions with Sn concentrations below 20%. Higher Sn concentration resulted in multi-phase composites. Initially, a drastic increase in the thermopower is observed for the composition with y = 0.01. Further increases in Sn concentration resulted in a gradual decrease in the thermopower. The highest power factor of 800 mu W/m . K-2 was obtained at 675 K for the composition with y = 0.1. This represents a 50% enhancement of the power factor when compared to the composition with y = 0.01 and is attributed to a large increase (700%) in the electrical conductivity and moderate reduction (57%) in the thermopower. This results in a similar to 34% improvement of the overall figure of merit with the highest ZT similar to 0.13 at 675 K for the composition with y = 0.1.

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