High temperature thermoelectric properties of skutterudite-Bi2Te3 nanocomposites

摘要

Nanocomposite engineering has been proved effective in diverse regimes of material research to attain a performance beyond each constituent phase. In this work, Yb-filled CoSb3 (bulk matrix/host)-Bi0.4Sb1.6Te3 (secondary inclusion) thermoelectric nanocomposites have been synthesized via an ex situ process. Bi0.4Sb1.6Te3 inclusions are mainly distributed at the grain boundaries of Yb0.2Co4Sb12 matrix in the composites. In particular, Te diffuses in situ from Bi0.4Sb1.6Te3 through Yb0.2Co4Sb12 matrix during the hot pressing process. This, combined with the grain boundary effect, results in favorable changes in the carrier concentration, carrier mobility, electrical resistivity, Seebeck coefficient, and thermal conductivity. Such synergistic changes are notably absent in the stand-alone Te-doped Yb-filled CoSb3, suggesting the key role of diffusion and grain boundaries. As a result, a maximum ZT value of 0.96 has been attained for Yb0.2Co4Sb12-2 wt Bi0.4Sb1.6Te3 at 650 K. The present work opens a new avenue towards high performance thermoelectric composites via controlled inter-constituent diffusion and grain boundary effect. (C) 2016 Elsevier Ltd. All rights reserved.