Nanostructure engineering has improved the performance of thermoelectric materials, but the deteriorated stability of the materials at high temperatures shortens the service life of thermoelectric modules. Here, we realized a...

As one kind of superionic conductor, CuAgSe is a promising thermoelectric material due to its extremely low thermal conductivity and high electron mobility. In this study, the electrical and thermal...

The thermoelectric figure of merit (ZT) in LaPtBi shows an overall increase with increasing hydrostatic pressure.

In this study, a series of Cu2+x–y In y Se (−0.3 ≤ x ≤ 0.2 and 0 ≤ y ≤ 0.05) samples were prepared by melting and the spark plasma sintering method. X-ray diffraction measurements indicate that the Cu-deficient samples (x = −0.3 y = 0 and x = −0.2 y = 0) prefer to form the cubic phase (β-Cu2Se). Adding excessive Cu or introducing In atoms into the Cu2Se matrix triggers a phase transition from the β to α phase. Positron lifetime measurements confirm the reduction in Cu vacancy concentration by adding excessive Cu or introducing In atoms into Cu2Se, which causes a dramatic decrease in carrier concentration from 1.59 × 1021 to 5.0 × 1019 cm–3 at room temperature. The samples with In contents of 0.01 and 0.03 show a high power factor of about 1 mW m–1 K–2 at room temperature due to the optimization of the carrier concentration. Meanwhile, the excess Cu content and doping of In atoms also favor the formation of nanopores. These pores have strong interaction with phonons, leading to remarkable reduction in lattice thermal conductivity. Finally, a high ZT value of about 1.44 is achieved at 873 K in the Cu1.99In0.01Se (x = 0 and y = 0.01) sample, which is about twice that of the Cu-deficient sample (Cu1.7Se). Our work provides a viable insight into tuning vacancy defects to improve efficiently the electrical and thermal transport performance for copper-based thermoelectric materials.

In this study, polycrystalline SnSe was synthesized via a rapid, cost-effective, and large-scale synthesis route. The obtained SnSe powders were pressed into pellets via spark plasma sintering (SPS) at different temperatures. Powder X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) were used to characterize the crystal structures and morphology of the SnSe samples. The XRD results indicate that the orientation factors increase monotonously with the increase of sintering temperature. The FESEM images show that sintering temperatures have no obvious influence on the particle size. Positron annihilation measurements indicate that vacancy defects exist in all the sintered SnSe samples, and they recover gradually with increasing sintering temperatures. These vacancy defects are responsible for the lower lattice thermal conductivity in samples sintered at lower temperatures. The electrical conductivity, power factor, thermal conductivity, and figure of merit ZT show nearly the same variation trend, which increases initially with the increasing sintering temperature up to 550 °C then decreases with further increase of the sintering temperature, which is possibly due to slight oxidation of SnSe. A maximum ZT value of ∼0.47 at 430 °C was achieved for the 550 °C sintered sample, which is higher than those reported for undoped polycrystalline SnSe around this temperature. Thus, we provide a simple, energy-saving, and effective method to synthesize polycrystalline SnSe in large quantities, and SPS is an effective method to optimize thermoelectric performance.

No abstract

Due to the ultrawide bandgap (4.9 eV), high carrier mobility (300 cm2V−1s−1), and high thermal stability, β−Ga2O3 can be a potential candidate for high-temperature thermoelectric materials. However, the intrinsically high thermal conductivity may hinder its application for thermoelectric conversion. In this work, porous β−Ga2O3 was prepared by the solvothermal method together with spark plasma sintering technology. Positron lifetime measurement and N2 adsorption confirm the introduction of pores by adding sucrose in the sample preparation. The sucrose-derived β−Ga2O3 sintered at a relatively low temperature of 600 °C remains highly porous, which results in an extremely low thermal conductivity of 0.45 W m−1K−1 at room temperature, and it further decreases to 0.29 W m−1K−1 at 600 °C. This is the lowest thermal conductivity for β−Ga2O3 reported so far. Our work provides an avenue to reduce the thermal conductivity for β−Ga2O3 and is believed to be widely applicable to many other thermoelectric materials.

Synergetic optimization of electrical and thermal transport properties is achieved for SnTe‐based nano‐crystalline materials. Gd doping is able to suppress the Sn vacancy, which is confirmed by positron annihilation measurements and corresponding theoretical calculations. Hence, the optimal hole carrier concentration is obtained, leading to the improvement of electrical transport performance and simultaneous decrease of electronic thermal conductivity. In addition, the incremental density of states effective mass m* in SnTe is realized by the promotion of the band convergence via Gd doping, which is further confirmed by the band structure calculation. Hence, the enhancement of the Seebeck coefficient is also achieved, leading to a high power factor of 2922 µW m−1 K−2 for Sn0.96Gd0.04Te at 900 K. Meanwhile, substantial suppression of the lattice thermal conductivity is observed in Gd‐doped SnTe, which is originated from enhanced phonon scattering by multiple processes including mass and strain fluctuations due to the Gd doping, scattering of grain boundaries, nano‐pores, and secondary phases induced by Gd doping. With the decreased phonon mean free path and reduced average phonon group velocity, a rather low lattice thermal conductivity is achieved. As a result, the synergetic optimization of the electric and thermal transport properties contributes to a rather high ZT value of ≈1.5 at 900 K, leading to the superior thermoelectric performance of SnTe‐based nanoscale polycrystalline materials.