Wavelength Dispersive X-ray Spectroscopy Research Articles

Impedimetric aptasensor for kanamycin by using carbon nanotubes modified with MoSe2 nanoflowers and gold nanoparticles as signal amplifiers.

An aptamer based impedimetric method is described for the determination of kanamycin. A hydrothermal route was applied to synthesize molybdenum selenide nanoflowers (MoSe2) which are promising materials for use in sensing interfaces due to their high specific surface and excellent electrical conductivity. Carbon nanotubes were then decorated with the MoSe2 nanoflowers and gold nanoparticles (AuNP/CNT/MoSe2) and placed on a glassy carbon electrode to serve as a signal amplifier. An amino-terminal kanamycin-specific aptamer was covalently linked to carboxy groups of acid-oxidized CNTs on the electrode to act as the signalling probe. The various steps during the construction of the modified electrode were monitored by scanning electron microscopy, wavelength-dispersive and energy-dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The change in electrochemical signal was quantified by electrochemical impedance spectroscopy, typically at a working voltage of 0.22V vs. Ag/AgCl. The calibration plot is linear in the 1 pM-0.1nM and 100nM-10μM kanamycin concentration range and has a 0.28 pM detection limit. The assay is outstandingly selective, sensitive, stable and reproducible. Graphical abstract ᅟ.

Reduction of hot cracking susceptibility during laser welding of aluminum by vibrations

Hot cracking is one of the main issues in welding of 6xxx aluminum alloys. Aim of this study is to identify the influence of applied vibrations on the hot cracking susceptibility during laser welding. Close-edge welding of EN AW-6082 sheets with and without vibrations was carried out. The total length of the centerline hot cracks and the resulting grain structure of the welds were determined. The silicon and magnesium element distributions were quantified by wavelength dispersive X-ray spectroscopy. The presence of low melting phases close to the centerline was analyzed by differential scanning calorimetry. The results show that the total length of hot cracks was significantly reduced by the applied vibration while the grain size and structure were not affected in the case of the used excitation conditions at a welding velocity of 6 m/min, whereas no significant influence was observed at lower welding velocities. The weld seams do not show an enrichment of silicon and magnesium close to the center line—macrosegregations—or an influence of the excitation on their distributions. The study shows that the avoidance of low melting phase compositions in the seam center is an influencing factor regarding the reduction of the hot cracking susceptibility by vibrations.

Immobilization of palladium nanoparticles on Metformin-functionalized graphene oxide as a heterogeneous and recyclable nanocatalyst for Suzuki coupling reactions and reduction of 4-nitrophenol

In this study, Pd nanoparticles supported on Metformin modified graphene oxide (GO-Met-Pd) is proposed as a green heterogeneous catalyst. The structural properties of the as-synthesized nanocatalyst were determined by X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), wavelength-dispersive X-ray spectroscopy (WDX) and inductively coupled plasma (ICP). Activity of the catalyst was investigated by focusing on the Suzuki-Miyaura coupling reaction and room-temperature reduction of 4-nitrophenol (4-NP), as model reactions. The catalyzed reactions provided high yields of biphenyl compounds through the Suzuki-Miyaura reaction and outlined highly efficient conversion of 4-NP to its reduced form. Moreover, no significant Pd leaching was detected in the reaction solutions and the catalyst could be recovered, at least, 6 times without any considerable loss of its catalytic activity.

Phase relations in the ternary system Ga–Pd–Sn at 500 °C

Phase relations in the ternary system Ga–Pd–Sn are presented in the complete concentration range at 500 °C. Binary phases of the terminating systems Ga–Pd and Pd–Sn show solubilities of 0–13 at.% Ga or Sn at constant Pd concentration, while isostructural phases GaPd2 and SnPd2 reveal complete mutual solubility at 66.7 at.% Pd. The only ternary phase has the homogeneity range at 60 at.% Pd with a composition Ga13–17Sn27–23Pd60. Phase analysis has been performed by means of X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) with energy dispersive and wavelength dispersive X-ray spectroscopy (EDXS and WDXS) as well as electron backscatter diffraction (EBSD). Microstructure analysis revealed considerably slow equilibration with increasing Pd content and showed significant variations in the habit of the solid solution Ga1−xSnxPd2.

Buchwald–Hartwig C–N cross coupling reactions catalyzed by palladium nanoparticles immobilized on thio modified-multi walled carbon nanotubes as heterogeneous and recyclable nanocatalyst

In current research, the multi walled carbon nanotubes was functionalized with mercapto-melamine groups by covalent grafting of f-CNT with ethylenediamine, cyanuric chloride and 2-mercaptoethanol for introducing mercapto functional groups on the surface of nanotube. Consequently, the thiolated MWCNTs were applied to deposing Pd nanoparticles. The results of FTIR, Raman spectroscopy, powder XRD, energy dispersive spectroscopy (EDS), wavelength-dispersive X-ray spectroscopy (WDX) and CHN analysis showed the successful synthesis of nanocatalyst. The scanning and transmission electron microscopes (SEM and TEM) were used to study the morphologies of the nanocatalyst. Moreover, the (MWCNTs/CC-SH/Pd) nanocatalyst was effectively applied in Buchwald–Hartwig C–N cross coupling reaction with wide variety of functionalized substrates. A variety of aryl amines were prepared through reaction of aryl halides (chloride, bromide and iodide) and amines in high yields. Remarkably, the new catalyst could be reused for six recycles without change in its catalytic activity.

Cu2ZnGe(S1-xSex)4 – The challenge to synthesize single phase material

The variation of the band gap energy in Cu2ZnGeSe4 and Cu2ZnGeS4 from 1.4 eV to 1.7 eV, which is controlled by different S/(S + Se) ratios renders the Cu2ZnGe(S1-xSex)4 solid solution an interesting material for the application in multi-junction solar cells. Nevertheless, this system has a certain complexity due to the existence of different polymorphs. Cu2ZnGeSe4 crystallizes in the tetragonal kesterite type structure, whereas Cu2ZnGeS4 may crystallize in the tetragonal stannite or the orthorhombic wurtz-stannite type structure, respectively.To gain deeper insights into this complex system a systematic study of the solid solution series Cu2ZnGe(S1-xSex)4 was performed using polycrystalline material prepared by solid state reaction. The chemical analysis performed by wavelength dispersive X-ray spectroscopy showed remarkable inhomogeneities with different quaternary phases co-existing within one sample. Additionally, a wide variety of binary and ternary secondary phases as well as elemental Ge was observed. The variety of secondary phases is higher in S-rich samples than in Se-rich samples of the solid solution. Thus, synthesis of Cu2ZnGe(S1-xSex)4 mixed crystals with off-stoichiometric composition is readily accompanied by the formation of various secondary phases making it a difficult task to obtain single phase material.

Catalytic reduction of 4-nitrophenol over Ag nanoparticles immobilized on Stachys lavandulifolia extract-modified multi walled carbon nanotubes

In current research, a new green process for modifying multi walled carbon nanotubes (MWCNTs) using extract of Stachys lavandulifolia as both stabilizer/capper and reductant agent was reported. The adsorbed biopolymers of S. lavandulifolia extract on the surface of CNTs can cause more in situ reduction of silver ions to silver nanoparticles and stabilize them. The physicochemical and structure features of the synthesized nanohybrid were studied in detail using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), wavelength-dispersive X-ray spectroscopy (WDX), inductively coupled plasma (ICP) and X-ray photoelectron spectroscopy (XPS). The achieved outcomes indicated the uniform distribution of Ag nanoparticles on the modified CNTs surface. The resultant MWCNTs@S. lavandulifolia/Ag nanocatalyst shows a superior catalytic behavior towards the reduction of 4-nitrophenol at ambient temperature with a great rate constant. The increased catalytic performance found with synthesized nanocatalyst is attributed to the CNTs surface coated with biopolymers of S. lavandulifolia extract which stabilizes and attracts the aryl nitro substrates adjacent to the catalytic places which in turn facilitates reducing nitro groups. The catalyst can be retained and reapplied seven times with no decrease in its catalytic performance.

Distribution of minor metallic elements within waste incineration bottom ashes defined by WDX/EDX spectrometry

Abstract. A number of metallic elements are inherited from waste during thermal treatment and concentrated in the incineration residues. Because the major part of the incineration residue mass are bottom ashes (BAs), their study is of great importance from the point of view of their environmental impact or resource potential. The general focus of this study was on the minor metallic elements present in BAs. They co-occurred with main phases and often determined the inherited potential of the material. The analysed residues were produced from municipal and industrial waste. The BAs were studied using spectroscopic methods of chemical microanalysis: energy dispersive X-ray spectrometry (EDX) and wavelength dispersive X-ray spectrometry (WDX). Both the main and minor metallic elements were concentrated in metallic components. They were typically present as separate grains and metallic inclusions (commonly in the glass matrix of the grains) ranging in size from several to hundreds of micrometres. Despite Fe-, Al- and Cu-rich occurrences, metallic elements rarely occurred in fragments composed of a single element. Their main forms of occurrence were alloy grains, admixtures in polymetallic occurrences and micro-inclusions in glassy matrix. The content of particular elements in those forms was investigated and described in greater detail. Even though two types of bottom ash were formed from different types of waste and differences in used technologies were present, the obtained materials contained metallic components having similar attributes. Elevated concentrations of not only Fe and Al, but also Ti, Cu and Zn, allow us to consider bottom ash as a promising material from the point of view of metallic elements' recovery (e.g. by the physical concentration of elements through gravity or magnetic methods).

Microstructure and thermal stability of Mo-(Ag)-N coatings with high nitrogen content

The interplay between the chemical composition and the microstructure of nitrogen-rich Mo-(Ag)-N coatings deposited by reactive magnetron sputtering was investigated using a combination of wavelength-dispersive X-ray spectroscopy, glancing-angle X-ray diffraction and transmission electron microscopy with high resolution. It was proven that the microstructure of the coatings, in particular the amount of hexagonal and cubic molybdenum nitrides, can be controlled by the nitrogen partial pressure in the deposition apparatus. In the as-deposited coatings, a metastable nitrogen-rich cubic phase of molybdenum nitride was detected, which decomposed into the thermodynamically stable cubic Mo2N and hexagonal MoN upon annealing at 600 °C. The mechanisms stabilizing the metastable cubic phase are discussed. Silver is only marginally soluble in the molybdenum nitrides, thus its addition leads mainly to the interruption of the growth of the Mo-N crystallites and to the grain refinement in the Mo-Ag-N coatings. The small amount of silver, which is incorporated into the crystal structure of the molybdenum nitrides, affects predominantly the thermal stability of the metastable cubic phase.

Comparison and Combination of Energy and Wavelength Dispersive X-Ray Spectrometry in Electron Probe Microanalysis of Minerals and Glasses

Comparison and Combination of Energy and Wavelength Dispersive X-Ray Spectrometry in Electron Probe Microanalysis of Minerals and Glasses

Preparation of Polydopamine Sulfamic Acid-Functionalized Silica Gel as Heterogeneous and Recyclable Nanocatalyst for Acetylation of Alcohols and Amines Under Solvent-Free Conditions

To fabricate SiO2/PDA–SO3H nanocatalyst, a suitable method is designed for the loading of sulfonic acid groups on the surface of polydopamine (PDA)-encapsulated SiO2 nanoparticles. To bridge the gap between heterogeneous and homogeneous catalysis, surface functionalization of silica gel is an elegant procedure. The morphology, structure, and physicochemical features were specified using different analytical techniques including field emission scanning electron microscopy (FESEM), Fourier transformed infrared spectroscopy (FT-IR), high resolution-transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDS), wavelength-dispersive X-ray spectroscopy (WDX), X-ray photoelectron spectroscopy (XPS), and back titration. The SiO2/PDA–SO3H nanoparticles are efficient nanocatalysts for the acetylation of many alcohols, phenols, and amines with acetic anhydride under solvent-free conditions in good to excellent yields. Moreover, the reuse and recovery of the catalyst was shown seven times without detectible loss in activity.

In situ immobilized palladium nanoparticles (Pd NPs) on fritillaria imperialis flower extract-modified graphene and their catalytic activity for reduction of 4-nitrophenol

Abstract In this study, a complete green synthesis method to reduced graphene oxide-Pd nanoparticles hybrid by applying extract of Fritillaria imperialis flower as both stabilizing and reducing agent was reported. Fritillaria imperialis flower extract reduce graphene oxide and adsorb on the reduced graphene oxide surface. Moreover, the surface adsorbed Fritillaria imperialis flower extract can more in situ reduce Pd ions to Pd nanoparticles and stabilize them. The physicochemical and structure properties of the produced nanohybrid were examined in detail by X-ray diffraction (XRD), UV–vis spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), wavelength-dispersive X-ray spectroscopy (WDX), inductively coupled plasma (ICP) and X-ray photoelectron spectroscopy (XPS). The obtained results showed that Pd nanoparticles uniformly distributed on the functionalized graphene surface. The catalytic efficiency of the resulting heterogeneous nanocatalyst (Pd NPs/FGO) was evaluated at room temperature for the 4-nitrophenol (4-NP) reduction in an environmental friendly medium. The enhanced catalytic activity observed with our nanocatalyst is attributed to the graphene surface's coated by biopolymers of Fritillaria imperialis flower extract which stabilizes and attracting the aryl nitro substrates adjacent to the catalytic sites which in turn facilitates the reduction of nitro groups. The catalyst was recycled by centrifugation and reapplied several times without any significant catalytic activity loss.

An Examination of the Composition and Microstructure of Coarse Intermetallic Particles in AA2099-T8, Including Li Detection.

Electron and proton microprobes, along with electron backscatter diffraction (EBSD) analysis were used to study the microstructure of the contemporary Al-Cu-Li alloy AA2099-T8. In electron probe microanalysis, wavelength and energy dispersive X-ray spectrometry were used in parallel with soft X-ray emission spectroscopy (SXES) to characterize the microstructure of AA2099-T8. The electron microprobe was able to identify five unique compositions for constituent intermetallic (IM) particles containing combinations of Al, Cu, Fe, Mn, and Zn. A sixth IM type was found to be rich in Ti and B (suggesting TiB2), and a seventh IM type contained Si. EBSD patterns for the five constituent IM particles containing Al, Cu, Fe, Mn, and Zn indicated that they were isomorphous with four phases in the 2xxx series aluminium alloys including Al6(Fe, Mn), Al13(Fe, Mn)4 (two slightly different compositions), Al37Cu2Fe12 and Al7Cu2Fe. SXES revealed that Li was present in some constituent IM particles. Al SXES mapping revealed an Al-enriched (i.e., Cu, Li-depleted) zone in the grain boundary network. From the EBSD analysis, the kernel average misorientation map showed higher levels of localized misorientation in this region, suggesting greater deformation or stored energy. Proton-induced X-ray emission revealed banding of the TiB2 IM particles and Cu inter-band enrichment.

Catalytic Oxidation of Volatile Organic Compounds by 13X Zeolite Coated with nZnO in Presence of UV and Ozone at High Bed Temperature

Catalytic oxidation of benzene, toluene, and ethylbenzene (BTE) on virgin zeolite, nZnO-coated zeolite, with and without UV + O3, at 300 °C bed temperature was investigated using laboratory experiments. The coating was done at three weight ratios of Zn (estimated Zn content in nZnO) to zeolite (0.2:1.0, 0.5:10, 1.0:1.0). The coated adsorbents were examined by scanning electron microscopy, wavelength dispersive X-ray spectroscopy, and Brunauer Emmett Teller analyses. In the catalytic oxidation experiments, the adsorbents were first saturated with BTE by purging an air stream containing a mixture of BTE at 5 ppm each for 28 min. Introduction of UV + O3 on the coated 13X zeolite (0.5:1.0) bed improved the average removal efficiency (RE) of benzene, toluene, and ethylbenzene (with inlet concentration of 5 ppm each) to 68.7, 90.0, and 99.6%, respectively, from the corresponding values of 57.3, 79.9, and 98.5% when no UV + O3 was used. An increase in the coating weight ratio from 0.2:1.0 to 0.5:1.0 had produced a higher RE for benzene only, while a further increase to 1.0:1.0 witnessed a decrease in RE for all three compounds, and more for benzene. Avg RE of BTE decreased with the increase in their inlet concentrations, more significantly for an increase from 5 to 50 ppm and less noticeable for a further increase to 100 ppm. The final oxidation products and intermediate products in the outlet streams from the oxidation and thermal desorption were analyzed which showed predominant compositions of CO2 followed by BTE and some levels of CO and other volatile organic compounds.

Enhanced photocatalytic degradation of doxycycline using a magnetic polymer-ZnO composite.

A novel magnetic polymer-ZnO composite was prepared by incorporating Fe3O4 and ZnO nano-particles in the structure of an adsorbent polymer. Precipitation polymerization was used for synthesizing the adsorbent polymer and its efficiency for extracting doxycycline from aqueous solution was optimized according to several parameters including time, pH and amount of polymer. Results showed the highest extraction efficiency at neutral pH of the doxycycline solution in 20 min, and the capacity of the polymer was about 20 mg/g. The magnetic property of a material is important for fast and facile separation of composite particles after each use. Magnetic polymer-ZnO composite was synthesized by adding Fe3O4 and ZnO nano-particles to the polymerization mixture in order to take advantage of both sorption and photocatalytic degradation mechanisms. The obtained composite was characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy equipped with wavelength dispersive X-ray spectroscopy and used for enhanced photocatalytic degradation of doxycycline in aqueous solution. Results showed 76.5% degradation of doxycycline in 6 hours which was significantly higher than the degradation observed by an equivalent amount of ZnO nano-particles. Photocatalytic degradation of doxycycline fitted the pseudo first order kinetic model with a rate constant of 4 × 10-3 μg mL-1 min-1.

Biosynthesis of CuO nanoparticles using Rosa canina fruit extract as a recyclable and heterogeneous nanocatalyst for C-N Ullmann coupling reactions

In a biological process where the Rosa canina fruit’s aqueous extract was applied as a capping and reducing agent, nanoparticles (NPs) of copper oxide (CuO) were synthesized. These CuO NPs were classified via X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), UV–visible spectroscopy, and wavelength-dispersive X-ray spectroscopy (WDX). These nanoparticles were used as appropriate suitable nanocatalyst for indole N-arylation, aniline and benzyl amine via Ullmann-type C-N coupling reactions. Enough to N-arylated products outstanding quantities were synthesized and the nanocatalyst was reusable and retrievable several (6) times without considerable decrease in catalytic efficiency.

(Invited) Electrochemical Methods for Surface Composition Determination of Alloy and Core/Shell Nanoparticles

The surface characteristics of metallic nanoparticles (NPs), especially the atomic percent and distribution of each component, is critical to their catalytic and electrocatalytic behavior. Therefore, efforts are underway to design NP catalysts with full control of their composition, both in the bulk and at the surface. In our work, Pt-Ru and Pt-Ir NPs, either in alloy or core@shell forms, are of great interest, due to their suitability for a wide range of electrocatalytic and sensing applications, such as for the oxidation of formic acid, alcohols, and ammonia, for oxygen evolution and reduction in regenerative fuel cells, in the reduction of hydrogen peroxide, and as an electron mediating matrix in glucose biosensors 1–8. In the present work, PtxIry alloys, Ircore@Ptshell, Rucore@Ptshell, and Rucore@Pt-Irshell NPs were synthesized using the simple and controllable polyol method 9. In the case of PtxIry alloy NPs, two sequential heating steps were employed to minimize the possibility of surface enrichment of Pt or Ir during NP formation. In the case of Ircore@Ptshell and Rucore@Ptshell NPs, the Ptshell, with a coverage of between 0.1 and 2 monolayers (MLs), was controllably deposited on the surface of the Ircore and Rucore NPs, while for the Rucore@Pt-Irshell NPs, one ML of the PtxIry alloy shell, containing different Pt:Ir ratios, was deposited on the Rucore. Wavelength dispersive X-ray spectroscopy (WDS) and energy dispersive X-ray spectroscopy, coupled with high-resolution transmission electron microscopy (EDS/HRTEM) and powder X-ray diffraction (PXRD), were then used to determine the bulk composition and homogeneity of the NPs. To determine the outer surface composition of these NPs, the underpotential deposition/stripping of Cu and oxalic acid oxidation have been used previously, e.g., for Pt-Ru NPs 10–12. However, the effect of NP size, Pt-Ru interactions at the surface, and the degree of Ru oxidation on the catalytic activity have not been determined. In other prior work 13, CO stripping was used to establish the stability of PtRu NPs by tracking the changes in the surface composition. In the present work, several electrochemical fingerprinting methods were developed (underpotential deposition/removal of H atoms, CO stripping, and surface oxide reduction) to determine the precise coverage and thickness (fraction of MLs) of the Ptshell on the Ircore@Ptshell and Rucore@Ptshell, NPs and the Pt:Ir ratio at the surface of the PtxIry alloy and Rucore/Pt-Irshell NPs, as well as the real surface area of the exposed metals. Figure 1 1,14,15 shows the CO stripping voltammetry of the NPs under study here as an example of how the peak potential and splitting correlate with the NP surface composition. A comparison will be given between the surface areas and compositions obtained by each of the electrochemical methods used here, as well as with what can be inferred from TEM imaging methods.

Investigation of nitrogen transport in active screen plasma nitriding processes – Uphill diffusion effect

The paper presents a structure of a nitrided layer formed with active screen plasma nitriding (ASPN) technique, which is a modification of plasma nitriding. The model investigated material was Fe Armco. The nitriding processes were carried out at 773 K for 6 h and 150 Pa. The main objective of this study was to confirm nitrogen migration effect and its influence on the nitride layer formation in different area of the layer interfaces (ε/ε+γ′/γ′). The results of the tests were evaluated using scanning electron microscopy (SEM, SEM/EBSD), transmission electron microscopy – electron energy loss spectroscopy (TEM-EFTEM), secondary ion mass spectroscopy (SIMS) and Wavelength Dispersive X-Ray Spectrometry (WDS). The analysis of the results suggests that the structures of the nitrided layers and nitrides morphology differ for various parameters and are dependent on the surface layer saturation mechanism for each of the temperatures and process parameters. New approaches in diffusion of nitrogen and carbon atoms and optimizing process were also analyzed. Nitrogen and also carbon transport in the sublayer was observed by several effects i.e. uphill diffusion effect which confirmed migration of the atoms in diffusive layer towards top surface (ε/ε+γ′ interface) and stress change effect in the nitrogen saturation area of the (Fe(C,N)+γ′) layer. Results showed in the paper might be used both for optimization of ASPN processes, modeling of nitrided layers formation mechanism and for controlling the nitrided layers morphology when nitriding different Fe based materials.

Pd(II)/Pd(0) anchored to magnetic nanoparticles (Fe3O4) modified with biguanidine-chitosan polymer as a novel nanocatalyst for Suzuki-Miyaura coupling reactions

This article is devoted to synthesis of a new magnetic interphase palladium catalyst that has been immobilized on chitosan-biguanidine coated-magnetic Fe3O4 nanoparticles [Pd(0/II)/CS-bigua@Fe3O4]. Such surface functionalization of magnetic particles is a promising method to bridge the gap between heterogeneous and homogeneous catalysis approaches. The structure, morphology, and physicochemical properties of the particles were characterized through different analytical techniques, including Fourier transformed infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), wavelength-dispersive X-ray spectroscopy (WDX), inductively coupled plasma (ICP), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Pd(0/II)/CS-bigua@Fe3O4 demonstrated high catalytic activity as a recyclable nanocatalyst toward Suzuki-Miyaura cross-coupling reactions, at room temperature. Furthermore, the catalyst could be recovered and reused several times with no significant palladium leaching or change in its activity.

Heat–Electric Power Conversion Without Temperature Difference Using Only n-Type Ba8Au x Si46−x Clathrate with Au Compositional Gradient

Thermoelectric power generation is typically based on the Seebeck effect under a temperature gradient. However, the heat flux generated by the temperature difference results in low conversion efficiency. Recently, we developed a heat–electric power conversion mechanism using a material consisting of a wide-bandgap n-type semiconductor, a narrow-bandgap intrinsic semiconductor, and a wide-bandgap p-type semiconductor. In this paper, we propose a heat–electric power conversion mechanism in the absence of a temperature difference using only n-type Ba8Au x Si46−x clathrate. Single-crystal Ba8Au x Si46−x clathrate with a Au compositional gradient was synthesized by Czochralski method. Based on the results of wavelength-dispersive x-ray spectroscopy and Seebeck coefficient measurements, the presence of a Au compositional gradient in the sample was confirmed. It also observed that the electrical properties changed gradually from wide-bandgap n-type to narrow-bandgap n-type. When the sample was heated in the absence of a temperature difference, the voltage generated was approximately 0.28 mV at 500°C. These results suggest that only an n-type semiconductor with a controlled bandgap can generate electric power in the absence of a temperature difference.