Multiple effects result in significantly improved thermoelectric figure-of-merit of InSb semiconductors via embedding metastable Ag/Pt nano particles

InSb-based semiconductors are potential thermoelectric (TE) materials in the medium temperature range due to their non-toxicity, abundance, excellent process compatibility and stable chemical properties. The mobility of pure InSb is as high as 10 4 –10 5 cm 2 V −1 s −1 , which results in the ultra-high power factor ( PF ). However, the lattice thermal conductivity ( κ l ) is also high because of the intrinsic strong chemical bonding, resulting in a low zT value (∼0.38, at 773 K). In this study, a feasible strategy was adopted to decrease the κ l of InSb by embedding Ag/Pt nano particles (NPs) into the InSb bulks. The κ l at 703 K was reduced to 2.37 W m −1 K −1 (decrease by ∼40.3%) on account of the enhanced phonon scattering after embedding 2.0% Ag/Pt NPs. Moreover, owing to the synergistic optimization of element doping and energy filtering effects, the PF at 703 K was improved to 5.66 × 10 −3 W m −1 K −2 in the InSb+2.0% Ag/Pt NPs sample, which is ∼63.1% higher than that of pristine InSb (3.47 × 10 −3 W m −1 K −2 ). Ultimately, a remarkably high zT value of 0.81 was achieved at 703 K in the InSb+2.0% Ag/Pt NPs sample, which is ∼92.9% higher than that of the pure InSb. Embedding metastable NPs to achieve multiple effects simultaneously, including the phonon scattering, element doping and energy filtering effects is a feasible means to enhance the zT values, which probably is applicable to other TE materials. The zT value of InSb was increased from 0.42 to 0.81 (∼92.9%) at 703 K via embedding Ag/Pt alloy NPs. Multiple effects, including element doping, energy filtering effect and phonon scattering effect have been demonstrated in the InSb composites, which increased the PF by ∼63.1% and reduced the κ L by ∼41.0%, simultaneously. Embedding the metastable NPs into matrix is a feasible means to improve the thermoelectric performance. • The PF at 703 K was enhanced by ∼63.1% owing to the element doping and energy filtering effects. • The κ l decreased by ∼40.3% due to the broadband phonon scattering effect after embedding Ag/Pt NPs. • The optimal zT value was increased from 0.42 to 0.81 (∼92.9%) at 703 K. • Embedding metastable Ag/Pt NPs can achieve multiple effects to enhance the zT values.