Boosting thermoelectric performance of BayCo4Sb12 by interlinking large-aspect-ratio silver nanowires at the triple junction of grain boundaries

Abstract

Decoupling electrons and phonons transport has been a major challenge for enhancing thermoelectric (TE) performance. Incorporation of guest nano-inclusions into host phases has been proven effective for enhanced phonon scattering but induces additional electron scattering, resulting in limited effect in the improvement of TE performance. Herein, one-dimensional high-conducting silver nanowires (AgNWs) with a large aspect ratio have been uniformly incorporated into Ba0.2Co4Sb12 matrix. The AgNWs become Y shaped at the triple junctions of the grain boundaries, which create more hetero-interfaces for tuning the TE properties. The semi-coherent hetero-interfaces minimized the electron scattering, and the large-aspect-ratio AgNWs facilitate their interlinks, thus remarkably promoting the carrier mobility due to the reduction of boundary potential barrier. Meanwhile, the AgNWs could form nano-meso-micro-scale defects on random cross-sectional planes due to random penetration angles, bringing in full-wavelength phonon scattering. In a combined effect, a peak zT of 1.24 was achieved, enhanced by ∼43%. The corresponding TE module exhibited a high conversion efficiency of ∼8%, among the highest ever reported. This work demonstrated an effective strategy for enhancing TE performance by incorporating one-dimensional large aspect ratio conducting nanowires into the host phases with simultaneous reduction of thermal conductivity and enhancement of electron mobility.