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Abstract: Core–shell heterogeneous CdTe/TiO2 nanorod arrays have been prepared by a two-step synthesis route through combined hydrothermal growth and magnetron sputtering. The composition and microstructure of the arrays were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), which show that CdTe nanograins coated on the surface of the single-crystalline TiO2 nanorod arrays to form a type-II heterostructure. Compared with TiO2 nanorod arrays, the spectrum absorption region of CdTe/TiO2 core–shell nanostructure is broadened from ultraviolet light to visible light. The photoelectrodes of CdTe/TiO2 nanorod arrays show better photoelectric properties than those of bare TiO2 nanorod arrays. The output power of CdTe/TiO2 nanorod arrays is 25 times higher than that of a bare TiO2 nanorod array. These results indicate that the photoelectrode of CdTe/TiO2 nanorod array has a promising application in solar cell. [Copyright &y& Elsevier]

Abstract: Oriented n-type bismuth telluride thin films with various layered nanostructures have been fabricated by radio-frequency (RF) magnetron sputtering. The crystal structures and microstructures of the films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The transport properties including carrier concentration, mobility, Seebeck coefficient and in-plane electrical conductivity were measured, which showed strong microstructure-dependent behaviors. The relationship between morphologies and transport properties of the films was explored. The optimal morphology and transport properties of films were obtained at the substrate temperature of 350°C under the pressure of 1.0Pa with oriented layered structure. Based on these results, a formation mechanism of these nanostructures is proposed and discussed. The interfaces and grain boundaries formed in these layered structures are beneficial to the reduction in thermal conductivity, which could result in potential TE films with high ZT value. [Copyright &y& Elsevier]

Abstract: The solid electrolyte Li0.5La0.5TiO3 (LLTO) with high lithium ion conductivity was prepared by the conventional solid-state reaction method, and those LLTO powders were mixed with inactive second phase (Al2O3, MgO, SiO2) to give composites. The microstructure and conductivity properties of the composite are investigated by using X-ray diffraction, scanning electron microscope and AC impedance method. Those prepared LLTO is cubic crystal with superstructure. All conductivities of LLTO-based composites decrease with the addition of Al2O3 or MgO, but the grain boundary conductivity increases with the addition of SiO2. [Copyright &y& Elsevier]

Bismuth telluride based alloys have been a class of important thermoelectric materials widely used in cooling devices around room temperature. In this work, a series of polycrystalline samples of ternary compounds in the SnTe–Bi2Te3 system were prepared by rapid quenching of the melt followed by a sintering procedure of compacted pellets. The electrical conductivity and Seebeck coefficient of samples with various compositions were measured from room temperature up to about 600 K. The measured results show that the transport properties strongly vary with the composition and temperature. The microstructure in this system shows randomly oriented fine plate-shaped grains with multi-layered structure. [Copyright &y& Elsevier]

Polycrystalline samples of the ternary compound Pb2Bi4Te5 were prepared by a solvothermal process based on the reaction between BiCl3, Pb(NO3)2, Te, and KBH4 in N,N-dimethylformamide (DMF), and followed by a post heat-treatment of compacted pellets. The microstructures of samples were characterized using XRD and SEM. The thermoelectric properties were determined by measuring the electric conductivity and the Seebeck coefficient. These samples show a disordered layered structure, with a maximum Seebeck coefficient of 84 μV/K around 520 K. [Copyright &y& Elsevier]

Mechanoluminescent ZnS:Mn phosphor should have a main crystalline structure of wurtzite to get stronger mechanoluminescence. However, preparations of ZnS:Mn with high wurtzite content usually require a high calcination temperature of 1050–1150 °C. Here, we propose an effective strategy of using ball milling premix to greatly reduce the preparation temperature of wurtzite-ZnS:Mn phosphors. X-ray diffraction shows that ZnS:Mn with more than 90 wt% of wurtzite content could be obtained at a calcination temperature of 800 °C, which is 250 °C lower than that without milling. Moreover, the photoluminescence (PL) and mechanoluminescence (ML) of ZnS:Mn phosphors synthesized with a proper milling duration can be considerably enhanced (an enhancement of ∼188% for PL, ∼422% for ML) than those without milling, which maybe correlative with the higher wurtzite content. These findings offer a practical strategy for the large-scale preparation of highly-mechanoluminescent ZnS:Mn and hold the potential to facilitate the development and production of other high-performance phosphors. [Display omitted] • Using ball milling premix to facilitate the phase transition in ZnS:Mn phosphor. • Revealing the influence of milling duration on the phase composition in ZnS:Mn. • Obtain better luminescent performance from ZnS:Mn calcined at lower temperature. • Revealing the relationship between the structure and luminescent property of ZnS:Mn. [ABSTRACT FROM AUTHOR]

The regeneration of Nd-Fe-B sludge is of great practical significance for achieving the sustainable development and recycling of rare earth elements. In this study, the in-situ regeneration of sludge was realized at a lower temperature of 850 °C via the mechanochemical approach based on ball-milling and Ca-reduction diffusion. Single-phase nanocrystalline magnetic powders with high coercivity were prepared by regulating the experimental parameters and rare earth elements. The grain size of Nd-Fe-B powder obtained by 5 wt% TbH x addition was 68.1 nm, with a high coercivity of 18.38 kOe. After purification and dehydrogenation, the coercivity was 6.68 kOe, and the coercivity mechanism was controlled by reverse magnetic domain nucleation. The low temperature in this study significantly reduced the energy consumption for the calcium reduction regeneration of sludge. It facilitated the preparation of nanocrystalline Nd-Fe-B powders with high coercivity, offering a new idea for recycling Nd-Fe-B sludge. [Display omitted] • Regenerated Nd-Fe-B powder was prepared from sludge via mechanochemical approach. • The regeneration process was realized at a relatively low temperature of 850 °C. • The prepared (Nd,Tb) 2 Fe 14 B nanocrystalline powders exhibit excellent coercivity. • The coercivity mechanism was controlled by reverse magnetic domain nucleation. [ABSTRACT FROM AUTHOR]

Abstract: Highly ordered one-dimensional CoFe2O4 nanowires array possesses unique properties due to the low-dimensional effect, which make it a wide range of potential applications. In this paper, ordered CoFe2O4 nanowires array was prepared by a modified sol–gel method using anodic aluminum oxide template. Microstructure analysis performed by X-ray diffraction, scanning electron microscope, transmission electron microscope, and Raman spectra indicated the crystallization of pure CoFe2O4 phase. The nanowires were constituted by polycrystalline CoFe2O4 nanograins with an average size of 15nm, which results in an increase of band gap as evidenced by photoluminescence spectra. Furthermore, we found that the CoFe2O4 nanowires were coated with amorphous Al2O3 forming a core–shell structure. The formation mechanism of this structure was discussed. The nanowires array preserved the good magnetic property of CoFe2O4 bulk material, showing the prospect for applications. [Copyright &y& Elsevier]

SnTe, an ideal lead-free substitute of PbTe, recently has attracted much attention for thermoelectric heat to electricity generation. Previous reports mainly focused on band engineering and all-scale phonon scattering for enhancing the thermoelectric performance of bulk SnTe. Herein, we adopt strategy of interface engineering to design oriented nanopillar structure in SnTe film via one-step thermal evaporation method. The analysis of the electrical and thermal properties illustrates that the SnTe film with highly oriented growth shows enhanced thermoelectric performance. The excellent properties are mainly attributed to the special nanopillar structure, which may facilitate the electrons' transport while significantly scatter the phonons. The maximum power factor of 19.8 μW cm −1 K −2 and the thermal conductivity of 3.54 W m −1 K −1 are obtained. This work provides a promising approach to enhance the thermoelectric performance of SnTe film, which can be easily extended to other thermoelectric films. [ABSTRACT FROM AUTHOR]

SnTe, one lead-free analogue of PbTe, has been paid attention in thermoelectric community because it has the similar rock-salt crystal structure and electronic band structure. However, SnTe possesses a very high total thermal conductivity (∼10.0 W m −1 K −1 at room temperature) and a mediocre ZT (∼0.2 at 723 K). In this study, to reduce its thermal conductivity, we prepare SnTe samples by melting reaction followed by mechanical alloying and spark plasma sintering. We demonstrate that both total thermal conductivity and lattice thermal conductivity can be considerably reduced through reducing particle size from micro-scale to nano-scale via facially mechanical alloying method. Experimental results show that the total thermal conductivity at room temperature can be reduced from ∼10 W m −1 K −1 for SnTe ingot to ∼3Wm −1 K −1 for SnTe with mechanical alloying 25 h. Correspondingly, the lattice thermal conductivity at room temperature was reduced from ∼5Wm −1 K −1 to ∼2Wm −1 K −1 . Combination of reduced thermal conductivity and moderate power factor, average ZT ave can be increased by 33.3%, from 0.09 for SnTe ingot to 0.12 for SnTe with nano-grain size. [ABSTRACT FROM AUTHOR]

In this paper, it was found that phonons/electrons travel across the (1 1 1)-preferred Ag nanowire array like a bullet with very few scattering, similarly to ballistic transport. Here highly ordered, high-crystal-quality, high-density Ag nanowire array was successfully fabricated by the simple magnetron sputtering method in a large scale. It is interesting to observe that high electrical conductivity and fast heat transfer behavior (455 W/m·K) of the vertically aligned Ag nanowire array is superior to that of the ordinary Ag film. The films have been integrated into low-dimension cross-plane devices using mask-assisted deposition technology. For the typical device with 50 pairs of p / n couples, the output voltage and maximum power were up to 100.5 mV and 168.3 μW, respectively, for a temperature difference of 5 K. The maximum power of the device with ordered Ag nanowire array electrode would be over 10 times larger than that of the device with ordinary structure Ag electrode. The cooling performance of the device with Ag nanowire array electrode was over 121% higher than that of the device with ordinary Ag film electrode at current of 150 mA. The growth and transport mechanisms of (1 1 1)-preferred Ag NW array electrode have been discussed. [ABSTRACT FROM AUTHOR]