High Thermoelectric Performance of ZnO by Coherent Phonon Scattering and Optimized Charge Transport

Abstract

ZnO is identified as a potentially attractive n‐type oxide thermoelectric material due to its abundance, nontoxicity, and a high degree of stability. However, working with ZnO is challenging due to its high thermal conductivity from its strong ionic bonds and low electrical conductivity due to its low charge concentrations. Here, it is demonstrated that the electrical and thermal transport properties of ZnO can be simultaneously improved via the successful doping of Al and ZnS coating. The ZnS coating in Al‐doped ZnO is observed and analyzed through microstructure and spectroscopic studies. The power factor for 1% ZnS‐coated Zn0.98Al0.02O is increased to ≈0.75 mW m−1 K−2 at 1073 K, 161% higher than pure ZnO. This enhancement in the power factor can be explained by the aliovalent Al3+ doping and modifications in intrinsic defects, leading to an increased carrier concentration. Interestingly, ZnS coating significantly reduces lattice thermal conductivity to ≈2.31 W m−1 K−1 at 1073 K for 2% ZnS‐coated Zn0.98Al0.02O, a 62% decrease over pure ZnO. This large reduction in lattice thermal conductivity can be elucidated based on coherent phonon scattering via Callaway's model. Overall, the figure of merit, zT, increases to 0.2 in 2% ZnS‐coated Zn0.98Al0.02O, which is 272% higher than pure ZnO at 1073 K.

Percolation Process-Mediated Rich Defects in Hole-Doped PbSe with Enhanced Thermoelectric Performance

“…The data of Ag-, Na-, and K- doped PbSe with p-type conduction from literature are also included for comparison. If we assume that carriers are mostly scattered by acoustic phonons, under a single parabolic band (SPB) model, − a Pisarenko plot with an effective mass ( m *) of 0.28 m e ( m e is the inertial mass of electrons) is obtained through the following expressions − where r denotes the scattering factor ( r = −1/2 for acoustic phonon scattering), k B , e, η, p , and F n (η) are Boltzmann constant, elementary charge, reduced Fermi level, carrier concentration, and Fermi integral, respectively. The calculated Pisarenko plot could reasonably describe the variations of S for almost all the samples except the Sn-containing ones, see the orange curve.…”

Enhancement of Thermoelectric Performance in Robust ZnO‐Based Composite Ceramics Driven by A Stepwise Optimization Strategy

“…d) Comparison of power factor extracted from previously reported ZnO‐based TE materials. [ 50–55 ] The temperature dependence of e) thermal conductivity, f) electron thermal conductivity, g) lattice thermal conductivity, and h) ZT for the fabricated ZnO ceramics.…”

“…d) Comparison of ZT value extracted from previously reported ZnO‐based TE materials. [ 50–55 ] e) Schematic diagram of the electron and phonon transport mechanisms of 2% nano‐Si 3 N 4 particles compositing the 3% SnO 2 ‐doped ZnO ceramics. f) The Vickers hardness of the typical fabricated ZnO ceramics under a load of 4.9 N and the corresponding microscopy images of indentation.…”

“…Besides, the S(T) of all the sample shows negative, suggesting an n-type conductive behavior. Interestingly, after compositing Si 3 N 4 nanoparticles in 3% SnO 2 -doped ZnO, |S| is remarkably enhanced by 57.7% from 67.1 μV•K −1 (sample 3-SnO 2 ) to 105.8 μV•K −1 (sample 2-Si 3 N 4 ) at 300 K coming from the introduced carrier filtering effect that will be discussed in detail later, while 𝜎 is decreased slightly, which may be ascribed to the [50][51][52][53][54][55] The temperature dependence of e) thermal conductivity, f) electron thermal conductivity, g) lattice thermal conductivity, and h) ZT for the fabricated ZnO ceramics.…”

Investigation of Mn Single and Co-Doping in Thermoelectric CoSb3-Skutterudite: A Way Toward a Beneficial Composite Effect

“…Other families of compounds, such as the oxide and sulfide compounds, also appear to be attractive due to their low cost and/or eco-friendlier compositions but still show relatively modest zT values . Among these families, there are ZnO, , some natural sulfide-based minerals such as the recent colusites Cu 26 T 2 M 6 S 32 (T = V, Nb, Ta, Cr, Mo, W, Ti; M = Ge, Sn, Sb) , to mention a few.…”