Enhanced Thermoelectric and Mechanical Performance in n-Type Yb-Filled Skutterudites through Aluminum Alloying

Abstract

Herein, we demonstrate a synergistic combination of novel mechanisms in aluminum (Al)-alloyed Yb 0.3 Co 4 Sb 12 -based thermoelectric materials to address both reduction in thermal conductivity and concomitant enhancement in power factor (PF). Upon Al alloying, CoAl nanoprecipitates are embedded in the matrix, leading to (1) significant local strain and thus intensified phonon scattering and (2) carrier injection because of interphase electron transfer. Moreover, by decreasing the Yb filling fraction, not only is the electronic thermal conductivity significantly suppressed but also the carrier concentration is modulated to the optimum range, thus resulting in the dramatically boosted PF, especially below 773 K. As a result, a peak ZT value of 1.36 at 873 K and ZT ave of 0.96 from 300 to 873 K were obtained in Yb 0.21 Co 4 Sb 12 /0.32CoAl. Last but not the least, the mechanical properties of the Al-alloyed samples were considerably improved through CoAl precipitate hardening, offering great potential for commercial applications.

Multiple-Filling-Induced Full-Spectrum Phonon Scattering and Band Convergence Leading to High-Performance n-Type Skutterudites

“…This is mainly due to the decrease in the total filling fraction with the increased Al content. At the same time, more precipitated (Al, Ga)­Co nanoparticles transfer electrons to the skutterudite matrix as the content of Al increases . Thus, all the multiple-filled samples present similar n H values, which fall into the optimal carrier concentration range of Co y Fe 4‑ y Sb 12 -based filled skutterudites …”

A review of CoSb3-based skutterudite thermoelectric materials

“…In addition, introducing nanoscale second-phase into CoSb 3 -based materials to form nanocomposites can not only significantly reduce the thermal conductivity, but also may significantly affect the mechanical properties [158,177,[197][198][199][200][201] of CoSb 3 -based materials. Rogl and Rogl [199] reviewed systematically that nanoparticles can obviously change the mechanical properties of skutterudite TE materials.…”

“…This is mainly due to the establishment of a resistance against crack growth, a pinning effect in the embedded skutterudite matrix and a stronger interface between skutterudite matrix and nanoscale second-phases. The mechanical properties of different kinds of CoSb 3 -based nanocomposites were obviously changed by introducing some nanoparticles like Yb 2 O 3 [158], TiN [181,200], CoAl [197], CoSi [179], and SiC [198]. Qin et al [177] prepared Yb 0.3 Co 4 Sb 12 with in situ formed CoSi nanoprecipitates by adding the extra Co and Si.…”

Phase Transitions, Structure Evolution, and Thermoelectric Properties Based on A2MnSb2 (A = Ca, Yb)

“…Complex crystal structures, dispersive bands, and nonclassical bonding interactions yield Zintl phases with intrinsic “phonon-glass, electron-crystal (PGEC)” nature, making great advantages for devising many well-known TE (thermoelectric) systems. − Layered structures often prove effective in the PGEC properties of compounds: not only do their two-dimensional (2D) anionic frameworks facilitate good electrical conductivity derived from high carrier mobility but also the cations serve as additional phonon scattering centers, contributing to the low thermal conductivity. , More importantly, because layered substructures spatially isolate the electron conduction path from the phonon scattering region, synergistic manipulation for electrical and thermal transport properties may be relatively easier to achieve in layered structures. The n-type Mg 3 Bi 2 -based compounds with the CaAl 2 Si 2 -type layered structure have attracted much attention because of their excellent TE properties at room temperature (RT) .…”