Toward high thermoelectric performance p-type FeSb2.2Te0.8via in situ formation of InSb nanoinclusions

Abstract

We synergistically optimized the thermoelectric properties of p-type skutterudite FeSb_2.2Te_0.8via a facile “electron-channel phonon-barrier” nanocompositing approach without invoking the conventional “filling-rattling” concept. The InSb nanoinclusions formed in situ at the grain boundaries of p-type FeSb_2.2Te_0.8 play multiple roles: the high carrier mobility of InSb mitigates the mobility degradation at the grain boundaries (in line with the “electron-channel”), while the added grain boundaries effectively scatter heat-carrying phonons (in line with “phonon-barrier”). As a result, the simultaneous carrier mobility enhancement and the lattice thermal conductivity reduction yield a high figure of merit ZT of ∼0.76 at 800 K in the 3 mol% InSb-containing FeSb_2.2Te_0.8 sample, outperforming any other unfilled p-type skutterudites reported so far. The interplay between the p-type FeSb_2.2Te_0.8 host matrix and the n-type InSb nanoinclusions was analyzed in view of their respective electronic band structures and also in the context of an effective medium model. These results confirm not only the feasibility of fabricating p-type skutterudite nanocomposites, but also the great promise of FeSb_2.2Te_0.8 as the p-leg material in large-scale production of skutterudite-based thermoelectric modules.