International audienceUltralow thermal conductivity is of great interest in a variety of fields, including thermoelectric energy conversion. We report, for the first time, experimental evidence that Ga-doping in SnTe may lower the lattice thermal conduction slightly below the theoretical amorphous minimum at high temperature. Such an effect is justified by the spontaneous formation of nanoprecipitates we characterized as GaTe. Remarkably, the introduction of Ga (2-10%) in SnTe also improves the electronic transport properties by activating several hole pockets in the multivalley valence band. Experimental results are supported by density functional theory calculations. The thermoelectric figure of merit, ZT, reaches similar to 1 at 873 K in Sn0.96Ga0.07Te, which corresponds to an similar to 80% improvement with respect to pure SnTe

No abstract

The nano-inclusion in a matrix effectively scatters phonons and the band bending effect at the interfaces can selectively scatter carriers, resulting in the enhancement of thermoelectric performance.

We investigated thermoelectric properties in K-doped quaternary compounds of (Pb1-xKxTe)0.70(PbSe)0.25(PbS)0.05 (x ≤ 0.03). In terms of two valence bands model, we argue that the L-band approaches to the Σ-band with increasing the K-doping concentration resulting in the increase of carrier concentration and effective mass of carrier due to the increase of band degeneracy. The effective K-doping by x = 0.02 and PbS substitution causes high power factor and low thermal conductivity, resulting in the comparatively high ZT value of 1.72 at 800 K. The low thermal conductivity for (Pb0.98K0.020Te)0.70(PbSe)0.25(PbS)0.05 compound is attributed from the lattice distortion and line dislocation in a phase of nano precipitation. By optimizing K-doping and PbS substitution, we achieved the enhancement of practical thermoelectric performance such as average ZTavg = 1.08, engineering (ZT)eng = 0.81, maximum efficiency ηmax = 11.63 %, and output power density Pd = 6.3 W cm -2 , with temperature difference ΔT = 500 K, which has practical applicability in waste heat power generation technologies.

This research proposes a new strategy for exploring high-performance thermoelectric materials by weak disordering of topological crystalline Dirac semimetals.

Topological insulators have attracted much interest in topological states of matter featuring unusual electrical conduction behaviors. It has been recently reported that a topological crystalline insulator could exhibit a high thermoelectric performance by breaking its crystal symmetry via chemical doping. Here, we investigate the multiple effects of Na, Se, and S alloying on thermoelectric properties of a topological crystalline insulator PbSnTe. The Na doping is known to be effective for breaking the crystalline mirror symmetry of PbSnTe. We demonstrate that simultaneous emergence of band convergence by Se alloying and nanostructuring by S doping enhance the power factor and decrease lattice thermal conductivity, respectively. Remarkably, the high power factor of 22.3 μW cm K at 800 K is achieved for Na 1%-doped PbSnTeSeS mainly due to a relatively high Seebeck coefficient via band convergence by Se alloying as well as the suppression of bipolar conduction at high temperatures by the increase of energy band gap. Furthermore, the lattice thermal conductivity is significantly suppressed by PbS nanoprecipitates without deteriorating the hole carrier mobility, ranging from 0.80 W m K for PbSnTe to 0.17 W m K at 300 K for PbSnTeSeS. As a result, the synergistically combined effects of breaking the crystalline mirror symmetry of topological crystalline insulator, band convergence, and nanostructuring for PbSnTeSe S ( x = 0, 0.05, 0.1, 0.2, and 0.95) give rise to an impressively high ZT of 1.59 at 800 K for x = 0.05. We suggest that the multiple doping in topological crystalline insulators is effective for improving the thermoelectric performance.

No abstract

No abstract