Simultaneously optimizing the independent thermoelectric properties in (Ti,Zr,Hf)(Co,Ni)Sb alloy by in situ forming InSb nanoinclusions

We report an induction-melting spark-plasma-sintering synthesis process of the nanocomposite material composed of (TiZrHf)(CoNi)Sb coarse grains and in situ formed InSb nanoinclusions that occur primarily on the grain boundaries. We were able to qualitatively control the amount of InSb nanoinclusions by varying the In and Sb contents in the starting materials. The effects of the nanoinclusion formation and the matrix–nanoinclusion boundaries on the thermoelectric properties have been studied and correlated. In particular, the nanoinclusion-induced electron injection and electron filtering mechanisms helped to simultaneously decrease the resistivity, enhance the Seebeck coefficient and reduce the thermal conductivity of the nanocomposite. A figure of merit of ZT ∼ 0.5 was attained at 820 K for the sample containing 1 at.% InSb nanoinclusions, which is a 160% improvement over the sample containing no nanoinclusions. The experimental results are discussed in the context of the effective medium model formerly proposed by Bergman and Fel.