Xiaolei Nie

Superparamagnetic enhancement of thermoelectric performance

The ability to control chemical and physical structuring at the nanometre scale is important for developing high-performance thermoelectric materials. Progress in this area has been achieved mainly by enhancing phonon scattering and consequently decreasing the thermal conductivity of the lattice through the design of either interface structures at nanometre or mesoscopic length scales or multiscale hierarchical architectures. A nanostructuring approach that enables electron transport as well as phonon transport to be manipulated could potentially lead to further enhancements in thermoelectric performance. Here we show that by embedding nanoparticles of a soft magnetic material in a thermoelectric matrix we achieve dual control of phonon- and electron-transport properties. The properties of the nanoparticles—in particular, their superparamagnetic behaviour (in which the nanoparticles can be magnetized similarly to a paramagnet under an external magnetic field)—lead to three kinds of thermoelectromagnetic effect: charge transfer from the magnetic inclusions to the matrix; multiple scattering of electrons by superparamagnetic fluctuations; and enhanced phonon scattering as a result of both the magnetic fluctuations and the nanostructures themselves. We show that together these effects can effectively manipulate electron and phonon transport at nanometre and mesoscopic length scales and thereby improve the thermoelectric performance of the resulting nanocomposites.

Nonlinear response behavior of Fe/Bi2Te2.7Se0.3 artificially tilted multilayer thermoelectric devices to thermal contact

The response behavior of artificially tilted multilayer thermoelectric devices (ATMTDs) to thermal radiation has been intensely investigated for remote thermal detection; however, their response behavior to thermal contact is still not well understood. In this letter, Fe/Bi2Te2.7Se0.3 ATMTDs have been fabricated by alternately stacking metallic Fe layers and Bi2Te2.7Se0.3 layers to reveal the response behavior to thermal contact. It was found that the transverse thermoelectric voltages (ΔVx) of the ATMTDs once contacting heat source were rapidly raised in the first seconds and then nonlinearly attenuated after reaching maximum ΔVx. A one-dimensional unsteady heat transfer model was proposed to reveal the attenuation process, which obeys an exponential variation and strongly depends on the heat source temperature. Using the ATMTDs as temperature sensors, the detection uncertainty can be less than 1 K. This work has demonstrated great potential application of the ATMTDs in the field of contact-type temperature detection.The response behavior of artificially tilted multilayer thermoelectric devices (ATMTDs) to thermal radiation has been intensely investigated for remote thermal detection; however, their response behavior to thermal contact is still not well understood. In this letter, Fe/Bi2Te2.7Se0.3 ATMTDs have been fabricated by alternately stacking metallic Fe layers and Bi2Te2.7Se0.3 layers to reveal the response behavior to thermal contact. It was found that the transverse thermoelectric voltages (ΔVx) of the ATMTDs once contacting heat source were rapidly raised in the first seconds and then nonlinearly attenuated after reaching maximum ΔVx. A one-dimensional unsteady heat transfer model was proposed to reveal the attenuation process, which obeys an exponential variation and strongly depends on the heat source temperature. Using the ATMTDs as temperature sensors, the detection uncertainty can be less than 1 K. This work has demonstrated great potential application of the ATMTDs in the field of contact-type temperat...

Simultaneously improved electrical properties of crystalline YbAl3 thin films prepared by co-sputtering technique

With the growing interest in developing miniaturized thermoelectric devices, there has been a strong demand in preparing thermoelectric thin films with high electrical conductivity and large power factors, hence ensuring the miniaturized devices have large cooling capacity and large output powers. This work demonstrated the preparation of intermetallic YbAl3 thin films through a double-target magnetron co-sputtering technique and a subsequent annealing treatment. It was revealed that the subsequent heat treatment of thin films plays a critical role in achieving crystalline, stoichiometric, and nanostructured YbAl3 thin films. Benefiting from the significantly improved crystallinity and stoichiometry, the optimized YbAl3 thin films exhibit extraordinarily high electrical conductivity reaching 1.7 × 106 S m−1 and large power factors around 7.4 mW m−1 K−2. The figure of merit ZT of the annealed thin films is comparable with that of the bulk materials, showing their potential use in miniaturized thermoelectric devices.

Corrigendum: Superparamagnetic enhancement of thermoelectric performance

This corrects the article DOI: 10.1038/nature23667