Effect of Cd isoelectronic substitution on thermoelectric properties of Zn0.995Na0.005Sb

AbstractZnSb as a kind of material with abundant resource and low cost has a low thermal conductivity and a high Seebeck coefficient, giving the potential of high thermoelectric properties. In this paper, Cd isoelectronic substitution was adopted to further improve the thermoelectric performance by reducing the lattice thermal conductivity of ZnSb. The results show that Cd substitution reduces the lattice thermal conductivity and increases the electrical conductivity. A high ZT value of 1.22 is achieved at 350 °C for Zn0.915Na0.005Cd0.08Sb

Towards tellurium-free thermoelectric modules for power generation from low-grade heat

Thermoelectric technology converts heat into electricity directly and is a promising source of clean electricity. Commercial thermoelectric modules have relied on Bi2Te3-based compounds because of their unparalleled thermoelectric properties at temperatures associated with low-grade heat (<550 K). However, the scarcity of elemental Te greatly limits the applicability of such modules. Here we report the performance of thermoelectric modules assembled from Bi2Te3-substitute compounds, including p-type MgAgSb and n-type Mg3(Sb,Bi)2, by using a simple, versatile, and thus scalable processing routine. For a temperature difference of ~250 K, whereas a single-stage module displayed a conversion efficiency of ~6.5%, a module using segmented n-type legs displayed a record efficiency of ~7.0% that is comparable to the state-of-the-art Bi2Te3-based thermoelectric modules. Our work demonstrates the feasibility and scalability of high-performance thermoelectric modules based on sustainable elements for recovering low-grade heat

Facile synthesis of multifunctional ZnFe2O4 nanoparticles in liquid polyols

Monodisperse water-soluble ZnFe O nanoparticles with the particle size of 6.3 nm and band gap of 2.04 eV were synthesized by a simple and inexpensive method based on a polyols method. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), UV-vis absorption spectrophotometer, Fourier transform infrared (FT-IR) spectrometer, fluorescence spectrometer, X-ray photoemission spectroscopy (XPS) and physical properties measurement system (PPMS). The ZnFe O nanoparticles display photoluminescence and exhibit excellent superparamagnetic properties at room temperature. Photocatalytic activity studies confirm the as-synthesized ZnFe O nanoparticles have photoactive property towards the photodegradeation of methyl orange in the aqueous solution. The photodecomposition rate of ZnFe O nanoparticles maintains the high value for the second time by retrieving the catalyst using the magnet. Thus, the multifunctional ZnFe O nanoparticles can be not only used in the biological application, but also served as recyclable photocatalysts

Efficient removal of heavy metal ions by thiol-functionalized superparamagnetic carbon nanotubes

Thiol-functionalized multiwall carbon nanotube/magnetite nanocomposites (CNTs/Fe O ) were synthesized, and were investigated by power X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectrometer, Fourier transform infrared spectroscopy, thermogravimetric analyses, BET analysis and physical properties measurement system. The results showed that the 3-mercaptopropyltriethoxysilane (MPTS) was successfully grafted on the surface of CNTs/Fe O nanocomposites. The as-synthesized thiol-functionalized CNTs/Fe O (MPTS-CNTs/Fe O ) nanocomposites exhibited superparamagnetic property and higher specific surface area than that of CNTs/Fe O nanocomposites at room temperature. The adsorption properties of Hg and Pb as a function of contact time, pH value and initial metal concentration were characterized by an inductively coupled plasma optical emission spectroscopy (ICP-OES). The pseudo-first-order kinetic equation could better than that of pseudo-second-order kinetic equation to describe the adsorption kinetics of the before and after thiol-functionalized nanocopmposites. The removal efficiency of CNTs/Fe O nanocomposites and MPTS-CNTs/Fe O nanocomposites was highly pH dependent and the optimal pH value for adsorption was 6.5. The adsorption isotherms of Hg and Pb by MPTS-CNTs/Fe O nanocomposites matched well with the Langmuir model with the maximum adsorption capacities of 65.52 and 65.40mg/g, respectively

Superconductivity and mechanical properties for LaFe1-xZnxAsO0.85F0.15

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Roles of interface engineering in performance optimization of skutterudite‐based thermoelectric materials

Abstract Interface engineering has prevailed in the thermoelectric field for decades, and related performance has achieved great progress. Therefore, an in‐depth understanding of the impacts of the interface effect on the thermoelectric transport parameters is of vital importance. In this paper, taking skutterudite‐based thermoelectric materials as typical examples, the formation mechanism and preparation process of various interface types, including 1D dislocations, 2D grain refinement, 3D nanocomposites, and micro‐nanopores, are briefly summarized. In addition, we also systemically highlight recently striking achievements related to interfacial design to reveal the distinctive effect of each interface structure on the transport behavior of carriers and phonons. Finally, existing challenges in the thermoelectric performance optimization achieved by interface engineering are pointed out, and an outlook for further thermoelectric research is presented

Structure and Transport Properties of the BiCuSeO-BiCuSO Solid Solution

In this paper, we report on the crystal structure and the electrical and thermal transport properties of the BiCuSe1−xSxO series. From the evolution of the structural parameters with the substitution rate, we can confidently conclude that a complete solid solution exists between the BiCuSeO and BiCuSO end members, without any miscibility gap. However, the decrease of the stability of the materials when increasing the sulfur fraction, with a simultaneous volatilization, makes it difficult to obtain S-rich samples in a single phase. The band gap of the materials linearly increases between 0.8 eV for BiCuSeO and 1.1 eV in BiCuSO, and the covalent character of the Cu-Ch (Ch = chalcogen element, namely S or Se here) bond slightly decreases when increasing the sulfur fraction. The thermal conductivity of the end members is nearly the same, but a significant decrease is observed for the samples belonging to the solid solution, which can be explained by point defect scattering due to atomic mass and radii fluctuations between Se and S. When increasing the sulfur fraction, the electrical resistivity of the samples strongly increases, which could be linked to an evolution of the energy of formation of copper vacancies, which act as acceptor dopants in these materials

Facile synthesis of MWCNT-ZnFe2O4 nanocomposites as anode materials for lithium ion batteries

Monodisperse ZnFe O nanoparticles with sizes less than 10 nm have been successfully assembled on multi-walled carbon nanotubes (MWCNTs) by in situ high-temperature decomposition of the precursor iron(iii) acetylacetonate, zinc acetate and MWCNTs in polyol solution. A possible formation mechanism was proposed, which suggests that the ZnFe O nanoparticles are formed on the surface of MWCNTs through an aggregation thermochemical reaction process between ZnO and γ-Fe O subparticles. It was found that the coverage density on the MWCNTs could be easily controlled by changing the concentration of the precursor. As anode materials for Li-ion batteries, the MWCNT-ZnFe O nanocomposites showed high rate capability and superior cycling stability with a specific capacity of 1152 mA h g , which was much higher than that of ZnFe O nanoparticles. The MWCNTs served as good electron conductors and volume buffers in improving the lithium performance of MWCNT-ZnFe O nanocomposites during the discharge-charge process. Magnetic measurements showed that the MWCNT-ZnFe O nanocomposites are superparamagnetic at room temperature and the magnetization of the samples can be controlled by the reaction conditions. The as-synthesized MWCNT-ZnFe O nanocomposites are water dispersible and can be manipulated by an external magnetic field. Therefore, the nanocomposites have significant potential for application in the fields of energy storage, composites, wastewater treatment and biomaterials