BiSbTe has been realized as an ideal p-type thermoelectric material near room temperature; however, its commercial applications are largely restricted by its n-type counterpart that exhibits relatively inferior thermoelectric performance.

Glitches correspond to sudden jumps of rotation frequency (ν) and its derivative ( ) of pulsars, the origin of which remains not well understood yet, partly because the jump processes of most glitches are not well time-resolved. There are three large glitches of the Crab pulsar, detected in 1989, 1996, and 2017, which were found to have delayed spin-up processes before the normal recovery processes. Here we report two additional glitches of this pulsar that occurred in 2004 and 2011 for which we discovered delayed spin-up processes, and present refined parameters of the largest glitch, which occurred in 2017. The initial rising time of the glitch is determined as <0.48 hr. The two glitches that occurred in 2004 and 2011 had delayed spin-up time scales (τ 1) of 1.7 ± 0.8 days and 1.6 ± 0.4 days, respectively. We also carried out a statistical study of these five glitches with observed spin-up processes. We find that the Δν versus relation of these five glitches is similar to those with no detected delayed spin-up process, indicating that they are similar to the others in nature except that they have larger amplitudes. For these five glitches, the amplitudes of the delayed spin-up process ( ) and recovery process (Δν d2), their time scales (τ 1, τ 2), and permanent changes in spin frequency (Δν p) and total frequency step (Δν g) have positive correlations. From these correlations, we suggest that the delayed spin-up processes are common for all glitches, but are too short and thus difficult to be detected for most glitches.

Cactus-shaped core double-shelled FeCo/C/Fe2.5Cr0.5Se4 nanostructures with a spiky surface were prepared by combining an arc-discharge process with a high-temperature solution chemical method.

The oxygen ion diffusion and phase transition in La2Mo2−xWxO9 (x=0, 0.25, 0.75, 1.0, and 1.4) have been investigated by the internal friction method. In addition to the low-temperature relaxation peak associated with oxygen ion diffusion, an internal friction peak of phase transition type is observed around 350°C in all tungsten substituted La2Mo2O9 compounds. Based on the behavior of this peak and the ionic conduction properties, the mechanism of this peak is suggested to be associated with a transition from static disordered state to dynamic disordered state of oxygen ion distribution in anion sublattice that most probably results in a transition of the ionic conduction from the Arrhenius type to the Vogel-Tamman-Fulcher type.

n-Type Bi 2 Te 2.7 Se 0.3 (BTS) is the state-of-the-art thermoelectric material near room temperature. However, the figure of merit ZT of commercial BTS ingots is still limited and further improvement is imperative for their wide applications. Here, the results show that through dispersion of the Ag 2 Te nanophase in BTS, one can not only elevate its power factor (PF) by as high as 14% (at 300 K) but also reduce its thermal conductivity κ tot to as small as ∼29% (at 300 K). Experimental evidences show that the improved PF comes from both increased electron mobility via inhibited Te vacancies and enhanced thermopower due to energy filtering effect, while the reduction of κ tot originates from the drop of both electronic thermal conductivity largely owing to the reduced number of vacancy V Te •• and intensified phonon scattering chiefly from the dispersed Ag 2 Te nanophase. Consequently, the largest ZT max = 1.31 (at 350 K) and average ZT ave = 1.16 (300−500 K) are achieved for the Bi 2 Te 2.7 Se 0.3 −0.3 wt % Ag 2 Te composite sample, leading to a projected conversion efficiency η = 8.3% (300−500 K). The present results demonstrate that incorporation of nanophase Ag 2 Te is an effective approach to boosting the thermoelectric performance of BTS. KEYWORDS: n-type Bi 2 Te 2.7 Se 0.3 , Ag 2 Te, thermoelectric material, power factor, phonon scattering

No abstract

The effects of tungsten doping in La2Mo2–x Wx O9 samples (x = 0, 0.1, 0.25, 0.5, 0.75, 1.0, 1.2, 1.4) were studied using dielectric relaxation measurements. Additional to the low‐temperature relaxation peak Pd associated with oxygen ion diffusion, a new dielectric loss peak Ph was observed around 740 K. With increasing tungsten concentration, the activation energy of peak Pd increases and saturates at a value of about 1.45 eV, and the height of peak Ph increases at first and then decreases after passing a maximum at 25% tungsten doping. With increasing measurement frequency, the height of peak Ph decreases monotonically but its position shifts very little. Peak Ph in pure and tungsten‐doped La2Mo2O9 is suggested to be associated with a phase transition from the static disordered state to the dynamic disordered state of oxygen ion/vacancy distribution. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

SnSe is considered as one of the most intriguing new thermoelectric materials. Polycrystalline SnSe offers a wide range of thermoelectric applications for its facile synthesis processing and machinability. Here, we...