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MoS 2 nanosheets with size of several-hundred nanometers were prepared by a hydrothermal intercalation/exfoliation method, then MoS 2 /Bi 2 Te 3 composite nanopowders were prepared by a microwave-assisted wet chemical method using the MoS 2 nanosheets, TeO 2 , Bi(NO 3 ) 3 ·5H 2 O, KOH and ethylene glycol as raw materials. Bulk MoS 2 /Bi 2 Te 3 nanocomposites were prepared by hot pressing the MoS 2 /Bi 2 Te 3 composite nanopowders with MoS 2 nanosheet content ranging from 0 to 17 wt% at 80 MPa and 648 K in vacuum. X-ray photoelectron spectroscopy and X-ray diffraction analyses indicate that MoS 2 and Bi 2 Te 3 did not react each other during the hot pressing. FESEM observation reveals that the MoS 2 /Bi 2 Te 3 composite samples had a more compact microstructure than the pristine Bi 2 Te 3 bulk sample. The MoS 2 phase was relatively randomly dispersed in the composite. At a given temperature, the electrical conductivity of the composites increases first then decreases as the MoS 2 content increases, whereas the Seebeck coefficient of the bulk nanocomposites does not change much. A highest power factor, ~18.3 μW cm −1 K −2 which is about 30% higher than that of pristine Bi 2 Te 3 sample, at 319 K has been achieved from a nanocomposite sample containing 6 wt% MoS 2 . [ABSTRACT FROM AUTHOR]

The ZT value is increased to ~1.05 at 723 K owing to the significant enhancement of the power factor and reduction in lattice thermal conductivity, making the ZT value of Ag 8 Ge 0.9 Sn 0.1 Se 6 stands among the highest in the Ag 8 GeSe 6 system at present. [Display omitted] • The carrier concentration and power factor are greatly improved upon Sn incorporation. • The lattice thermal conductivity decreases simultaneously. • The ZT value of Ag 8 Ge 0.9 Sn 0.1 Se 6 is increased to ~1.05. Argyrodite compound Ag 8 GeSe 6 (AGS) as one of the superionic conductors possesses unique crystal structures: the rigid anionic framework [GeSe 4 ]4- and mobile cation (Ag). Hence its lattice thermal conductivity is rather low due to the action of the mobile cation (Ag). However, this compound has neither high carrier concentration (0.15 × 1016 cm−3 at 300 K and 0.61 × 1016 cm−3 at 370 K) nor high thermoelectric performance (the figure of the merit (ZT) of<0.4). So in this work, we enhance the carrier concentration by more than one order of magnitude at 373 K through the band structure engineering via the substitution of Sn for Ge. In the mean time, the lattice thermal conductivity (κ L) reduces from 0.26 W/mK to 0.16 W/mK at 750 K. As a consequence, the ZT value of Ag 8 Ge 0.9 Sn 0.1 Se 6 is boosted to ~ 1.05. This value is about 2.8 times that of the pristine AGS (0.38 at 750 K) and stands among the highest in this family so far. The above results confirm that the isoelectronic substitution of Sn for Ge in the anionic framework of AGS is an effective way to realize its high TE performance. [ABSTRACT FROM AUTHOR]