T.J. Zhu

Transport properties of β-Zn4Sb3 prepared by vacuum melting

Abstract In this paper, single-phase polycrystalline β-Zn 4 Sb 3 samples were prepared by vacuum melting, and subjected to characterization using X-ray diffraction. The transport properties of the samples were measured between room temperature and 723 K. The power factor was found to be high between 500 and 650 K, and a maximum value of 3.9×10 −4 W m −1 K −2 was obtained at 623 K. The result suggested that this relatively inexpensive material is very promising for thermoelectric applications.

Electrochemical properties of some Sb or Te based alloys for candidate anode materials of lithium-ion batteries

Some antimony or tellurium based thermoelectric alloys have been prepared and studied as new candidate anode materials for lithium-ion batteries. It was found that some thermoelectric antimonides yield a volume capacity for reversible lithium storage more than twice that of state of the art carbon based materials. Ex-situ XRD analyses show that the semimetals such as antimony, bismuth and tellurium in the semiconducting thermoelectric alloys are the active elements for the lithium adsorption. However, inactive elements are also necessary for an alloy electrode to ensure the electrochemical capacity retention during cycling.

Thermoelectric properties of Bi0.5Sb1.5Te3/polyaniline hybrids prepared by mechanical blending

Abstract Thermoelectric hybrid materials consisting of Bi0.5Sb1.5Te3 and 1–7 wt.% polyaniline (PAn) have been prepared by mechanical blending and cold pressing. It is found that the Seebeck coefficients of the hybrid materials are about 10% lower than the Bi0.5Sb1.5Te3 sample. It is shown that the power factors of the hybrid materials decrease significantly with the increase of the polymer content due to mainly the decline of electric conductivities.

Transport properties of rapid solidified Fe–Si–Mn–Cu thermoelectric alloys

Abstract Manganese and cooper doped FeSi2 and Fe2Si5 alloys were prepared by a rapid solidification technique. X-ray diffraction analysis showed that the as-solidified FeSi2 alloy is composed of α-Fe2Si5 and e-FeSi phases, while only the α-Fe2Si5 phase exists in the as-solidified Fe2Si5 alloy. The semiconducting phase β-FeSi2 has not been found in the as-solidified structures but was obtained after annealing for 21 h at 800°C for both alloys. It was found that the excess silicon over the stoichiometric silicon content of the β-FeSi2 phase could improve the transport properties of the materials.

Strain effect on the surface potential and nanoscale switching characteristics of multiferroic BiFeO3 thin films

The BiFeO3 films were deposited on the SrTiO3 (001) substrates via tuning the thickness of the SrRuO3 (SRO) bottom electrode by pulsed laser deposition. The macroscopic ferroelectric and dielectric properties were dramatically impacted by the various nanoscale domain structures for both films due to the tunable SRO thickness. The nanoscale domain switching behaviors for both films were investigated via piezoresponse force microscopy, and results suggest that the domain structure could be changed by tuning the strain state. The surface potential investigation indicates that strain helps increase data storage density and stability.

Thermoelelctric properties of nanostructured skutterudite-related compounds

Nanostructuring is one of the effective approaches to lower the thermal conductivity of materials. Nanostructured skutterudite-related compounds CoSb₃, Fe_0.5Ni_0.5Sb₃, Fe_0.25Ni_0.25Co_0.5Sb₃ and Te-doped CoSb₃ were synthesized by a solvothermal route. The bulk materials were prepared by hot pressing or spark plasma sintering from the solvothermally synthesized nanopowders. The thermal conductivity values of the materials are decreased, which is mainly contributed to the small grain sizes and the high porosity. A thermoelectric figure of merit of 0.61 has been obtained for CoSb₃, which is notably high for the unfilled skutterudites. Filled skutterudites La_0.3Co₄Sb₁₂ and La_0.3FeCo₃Sb₁₂ were also synthesized by solvothermally process followed by annealing under hydrogen atmosphere. The thermoelectric properties are presented and discussed.

Nanostructuring and thermoelectric properties of semiconductor tellurides

Bulk nanostructured (Bi,Sb)2Te3 compounds and GeTe based amorphous/nanocrystal composites have been successfully fabricated by the combined hydrothermal/hot-pressing and quenching/annealing methods, respectively. The (Bi,Sb)2Te3 nanopowders synthesized by hydrothermal method exhibit a hollow-like structure. After hot-pressing, the nanoscale grains varying from tens to hundreds of nanometers were found in the bulk sample. The maximum ZT value of this (Bi,Sb)2Te3 sample is higher than the zone-melt one at room temperature. The sizes of the nanocrystals in the bulk GeTe nanocomposites were below 10 nm, the presence of which contributed to the remarkable improvement of the electrical conductivity and thermoelectric power factor compared to the amorphous precursors.