Effects of the Zr0.5Hf0.5FexCo1−xSb0.8Sn0.2/Fe3Sn2 half-Heusler composites on the ZT value

This study aims to evaluate the effect of a composite on the microstructures and the half-Heusler Zr0.5Hf0.5FexCo1−xSn0.2Sb0.8/Fe3Sn2 (x = 0.05, 0.1 and 0.2) on the ZT value. We demonstrate that the substitution of Fe for the Co site in Zr0.5Hf0.5FexCo1−xSn0.2Sb0.8 under the arc melting process is able to promote the occurrence of a second Fe3Sn2 phase. The in-situ formed Fe3Sn2 phase was evenly dispersed on the grain boundaries and increased with increasing amounts of Fe. Such structure morphology can be treated as Zr0.5Hf0.5FexCo1−xSn0.2Sb0.8/Fe3Sn2 (x = 0.05, 0.1 and 0.2) composites. The maximum substitution of the Co site by Fe is approximately 3.32 at.%. The effects of Fe doping on the Seebeck coefficient, electrical conductivity, and thermal conductivity of Zr0.5Hf0.5FexCo1−xSn0.2Sb0.8/Fe3Sn2 (x = 0.05, 0.1 and 0.2) composites have been investigated from 300 K to 900 K. The substitution of the Co site by Fe in Zr0.5Hf0.5FexCo1−xSn0.2Sb0.8 is effective in increasing the ZT value. The maximum ZT of Zr0.5Hf0.5Fe0.1Co0.9Sb0.8Sn0.2/Fe3Sn2 can reach 0.62 at 900 K after BM-SPS processing.