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.

High performance Bi2Te3 bulk materials with layered nanostructure have been prepared by combining melt spinning technique with spark plasma sintering, and their thermoelectric transport properties are investigated. The electrical conductivity increases greatly and the lattice thermal conductivity decreases significantly with the increase of the roller’s linear speed. These lead to a great improvement in the thermoelectric figure of merit (ZT). The maximum ZT value of 1.35 is obtained at 300K for the sample which is prepared by melt spinning with roller linear speed of 40m∕s. Compared with the zone melting sample, it increases by 73% at the same temperature.

P‐type polycrystalline SnSe and K0.01Sn0.99Se are prepared by combining mechanical alloying (MA) and spark plasma sintering (SPS). The highest ZT of ≈0.65 is obtained at 773 K for undoped SnSe by optimizing the MA time. To enhance the electrical transport properties of SnSe, K is selected as an effective dopant. It is found that the maximal power factor can be enhanced significantly from ≈280 μW m−1 K−2 for undoped SnSe to ≈350 μW m−1 K−2 for K‐doped SnSe. It is also observed that the thermal conductivity of polycrystalline SnSe can be enhanced if the SnSe powders are slightly oxidized. Surprisingly, after K doping, the absence of Sn oxides at grain boundaries and the presence of coherent nanoprecipitates in the SnSe matrix contribute to an impressively low lattice thermal conductivity of ≈0.20 W m−1 K−1 at 773 K along the sample section perpendicular to pressing direction of SPS. This extremely low lattice thermal conductivity coupled with the enhanced power factor results in a record high ZT of ≈1.1 at 773 K along this direction in polycrystalline SnSe.

We report a successful observation of pressure-induced superconductivity in a topological compound Bi 2 Te 3 with T c of ∼3 K between 3 to 6 GPa. The combined high-pressure structure investigations with synchrotron radiation indicated that the superconductivity occurred at the ambient phase without crystal structure phase transition. The Hall effects measurements indicated the holetype carrier in the pressure-induced superconducting Bi 2 Te 3 single crystal. Consequently, the first-principles calculations based on the structural data obtained by the Rietveld refinement of X-ray diffraction patterns at high pressure showed that the electronic structure under pressure remained topologically nontrivial. The results suggested that topological superconductivity can be realized in Bi 2 Te 3 due to the proximity effect between superconducting bulk states and Dirac-type surface states. We also discuss the possibility that the bulk state could be a topological superconductor.high-pressure effects | pressure-tuned conductivity | topological superconductors U tilizing high pressure can be a very powerful method to generate new materials states, as demonstrated by either highpressure synthesis of new compounds, or pressure-tuned unique electronic states, such as insulator metal transitions. High pressure is particularly effective in tuning superconductivity as it is well documented that the record high superconducting transition temperature T c for either elements (1) or compounds (2) is created with the application of pressure. Recently, topological insulators (TIs) have generated great interest in the area of condensed matter physics (3-8). These materials have an insulating gap in the bulk, while also possessing conducting gapless edges or surface states in the boundaries that are protected by the timereversal symmetry (8, 9). Similar to TIs, topological superconductors have a full pairing gap in the bulk and gapless Majorana states on the edge or surface (10-13, 18). Majorana Fermions (14), half of ordinary Dirac fermions, could be very useful in topological quantum computing (15-17), which is proscriptive for new concept information technology.

Superparamagnetic Fe3O4 nanoparticles remarkably enhance the room-temperature thermoelectric and cooling performance of BiSbTe alloys.