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

Abstract

ZnO is a promising high‐temperature thermoelectric (TE) material due to its superior stability and earth abundance. However, the coupling relation between Seebeck coefficient and electrical conductivity on carrier concentration limits the optimum TE performance for most TE materials, especially ZnO. Herein, enhancement of TE performance is achieved via a stepwise optimization strategy composed of carrier concentration optimization and carrier filtering effect for fabricating robust ZnO‐based composite ceramics through a self‐developed specific high‐pressure synthesis followed by spark plasma sintering. Specifically, doping SnO2 provide substantial electrons to surge the carrier concentration. The subsequent compositing Si3N4 nanoparticles results in the unique reaction‐generated Zn2SiO4 nanoprecipitates with a larger bandgap and intrinsically low thermal conductivity, which introduce an excellent carrier filtering effect to increase the Seebeck coefficient by 57.7% at 300 K without compromising electrical conductivity much and enhance phonon scattering to cause an ultralow lattice thermal conductivity of 1.39 W m−1 K−1 achieving amorphous limits of ZnO (1.4±0.1 W m−1 K−1). Consequently, a high peak ZT (figure of merit) of 0.691 at 873 K is obtained, which is higher than that of previously reported ZnO‐based TE materials. This work demonstrates a feasible and effective strategy to fabricate high‐performance TE materials, especially those with inferior electrical conductivity.

High-pressure induces topology boosting thermoelectric performance of Bi2Te3

“…Substitute each of above parameters gives a binary relationship of κ L as a function of temperature and pressure respectively, as shown in figure 8(a). However, the introducing of massive defects in turn inevitably brings about an aggravation of phonon scattering [34], so the actual κ L may not be as high as we estimate here. The κ e is given by Wiedemann-Frantz's law:…”

“…There are plenty of dislocations and lattice distortions in Bi 2 Te 3 with HPHT preprocessed. In fact, these are typical lattice dislocations introduced by the shear of inter-grains with the processes of increasing pressure, which can be partially retained by the rapid high-pressure quenching [34,42,43]. The FFT and IFFT patterns of this grain in the standard case are shown at region 1 in figure 4(b).…”

“…Fabricating lattice distortions in the structure may be an effective way to induce enhanced ETT under pressure in Bi 2 Te 3 . Because lattice distortions can result inner localized chemical stress of compression or stretch, which constructs a localized non-hydrostatic pressure [33,34]. And according to previous works, non-hydrostatic pressure is more prone to ETT phenomena [35,36].…”