The anharmonic lattice dynamics of rock-salt thermoelectric compounds SnTe and PbTe are investigated with inelastic neutron scattering (INS) and first-principles calculations. The experiments show that, surprisingly, although SnTe is closer to the ferroelectric instability, phonon spectra in PbTe exhibit a more anharmonic character. This behavior is reproduced in first-principles calculations of the temperature-dependent phonon self-energy. Our simulations reveal how the nesting of phonon dispersions induces prominent features in the self-energy, which account for the measured INS spectra and their temperature dependence. We establish that the phase space for three-phonon scattering processes, combined with the proximity to the lattice instability, is the mechanism determining the complex spectrum of the transverse-optic ferroelectric mode.

Phonon self-energy and origin of anomalous neutron scattering spectra in SnTe and PbTe thermoelectrics

Development of the high performance thermoelectric unicouple based on Bi2Te3 compounds

As the first-generation semiconductor, silicon (Si) exhibits promising prospects in thermoelectric (TE) convention application with the advantages of un-toxic, abundant, robust, and compliant to the integrated circuit. However, Si-based TE materials are always implemented for high-temperature application and deficient at room temperature (RT) ambience. This study displays an N-type Si1−x−yGexSny thin film by carrying out the strategy of metallic modulation doping for enhancing its power factor (PF). It was distinct to observe the extra carriers poured from the precipitated Sn particles without prominent degradation of mobility while sustaining appreciable thermal conductivity. The PF of 12.21  μW cm−1 K−2 and zT of 0.27 were achieved at 125 °C, which illustrated the significant potential for implementation at near RT ambiance.

Reinforcement of power factor in N-type multiphase thin film of Si1−x−yGexSny by mitigating the opposing behavior of Seebeck coefficient and electrical conductivity

A review on energy conversion using hybrid photovoltaic and thermoelectric systems

By adding aluminium (Al) into lead selenide (PbSe), we successfully prepared n-type PbSe thermoelectric materials with a figure-of-merit (ZT) of 1.3 at 850 K. Such a high ZT is achieved by a combination of high Seebeck coefficient caused by very possibly the resonant states in the conduction band created by Al dopant and low thermal conductivity from nanosized phonon scattering centers.

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Enhancement of Thermoelectric Figure-of-Merit by Resonant States of Aluminum Doping in Lead Selenide

Solid-state energy conversion through thermoelectric effects remains the technology of choice for space applications for which, their low energy conversion efficiency is largely outweighed by the reliability and technical requirements of the mission. Radioisotope thermoelectric generators (RTGs) enable the direct conversion of the heat released by nuclear fuel into the electrical power required to energize the scientific instruments. The optimization of the conversion efficiency is intimately connected to the performances of the thermoelectric materials integrated which are governed by the transport properties of these materials. Recent advances in the design of highly efficient thermoelectric materials raise interesting prospects to further enhance the performances of RTGs for future exploratory missions in the Solar system. Here, we briefly review the knowledge acquired over the last years on several families of thermoelectric materials, the performances of which are close or even higher than those conventionally used in RTGs to date. Issues that remain to be solved are further discussed.

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Thermoelectric materials for space applications

Chalcogenide semiconductors continue to be of prime interest for designing novel efficient materials for energy-conversion applications. Among them, the narrow-band-gap p-type semiconductor InTe exhibits high thermoelectric performance that mostly stems from its poor ability to transport heat. Here, we show that its thermoelectric figure of merit can be further enhanced by finely tuning the hole concentration through Pb doping. X-ray diffraction and scanning electron microscopy performed on the polycrystalline series In1−xPbxTe confirm that Pb substitutes for In with an estimated solubility limit below 1%. Pb acts as a donor-like impurity, driving the degenerate behavior of pristine InTe towards semiconducting-like properties. The enhanced disorder caused by this substitution increases point-defect scattering of phonons, leading to reduced lattice thermal conductivity. The resulting increase in the power factor and decrease in the phonon transport to values as low as 0.22 W m−1 K−1 above 700 K yields a peak ZT value of 1.05 at 780 K for x = 0.1% along the direction parallel to the pressing direction. According to a single parabolic band model, this sample exhibits a near-optimal thermoelectric performance.

Enhanced thermoelectric performance of InTe through Pb doping

Mo-based cluster compounds form a large class of materials with interesting thermoelectric properties primarily due to their very low lattice thermal conductivity. Here, we investigate the influence of the insertion...

Adèle Léon

Papers

Thermoelectric materials for space applications

Enhanced thermoelectric performance of InTe through Pb doping

Influence of Cu insertion on the thermoelectric properties of the quaternary cluster compounds Cu3M2Mo15Se19 (M = In, K) and Cu4In2Mo15Se19