High
thermoelectric performance and low material cost are essential
to the commercialization of thermoelectric modules. Microstructural
design, size effects, and rational band engineering are among the
keys to high thermoelectric performance, especially for nanocomposites.
Here, we demonstrate a facile and versatile bottom-up approach to
produce nanocomposites by heat consolidating solution-processed PbSe
nanoparticles with a proper amount of Ag. In this PbSe-Ag system,
a certain amount of Ag diffuses into the PbSe matrix and partially
substituted Pb while other forms Ag2Se at the interphases.
This increased the electrical conductivity and inversed the n-type behavior of PbSe to p-type, which
is observed from the positive Seebeck coefficient for PbSe-Ag nanocomposites
over the temperature range. Nonetheless, the decrease of total lattice
thermal conductivity at high temperature is ascribed to the effective
phonon at grain boundaries, Ag2Se nanodomain, and point
defect. Overall, we obtained an optimized figure of merit, ZT = 0.97
at 723 K for 5 wt % Ag, a significant improvement of 8.8 times than
the pure PbSe. Thus, this partially substituting host atom and the
presence of a secondary phase provide another potential strategy to
enhance the thermoelectric performance of PbSe, promoting its commercialization.
Multifarious defects are introduced in SnTe by CuSbSe2 alloying to induce full-scale phonon scattering, which leads to an ultra-low lattice thermal conductivity, reaching the amorphous limit, and achieves prominent thermoelectric performance.
Recently, ternary Cu-based Cu-IV-Se (IV = Sb, Ge, and Sn) compounds have received extensive attention in the thermoelectric field. Compared with Cu-Sb-Se and Cu-Sn-Se, Cu-Ge-Se compounds have been less studied due to its poor Seebeck coefficient and high thermal conductivity. Here, the Cu 2 GeSe 3 material with high electrical conductivity was first prepared, and then, its effective mass was increased by doping with S, which led to the Seebeck coefficient of the doped sample being 1.93 times higher than that of pristine Cu 2 GeSe 3 at room temperature. Moreover, alloying Ag at the Cu site in the Cu 2 GeSe 2.96 S 0.04 sample could further cause a 5.16 times increase in the Seebeck coefficient at room temperature, and the lattice thermal conductivity was remarkably decreased because of the introduction of the dislocations in the Cu 2 GeSe 3 sample. Finally, benefitted from the high Seebeck coefficient and low thermal conductivity, a record high ZT = 0.9 at 723 K was obtained for the Cu 1.85 Ag 0.15 GeSe 2.96 S 0.04 sample, which increased 345% in comparison with the pristine Cu 2 GeSe 3 , and it is among the highest reported values for Cu 2 GeSe 3based thermoelectric.
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