Studying Thermoelectric Power Behaviors of Bi2Te3 Nanoparticles Prepared by Thermal Evaporation

Thin films of Bismuth Telluride (Bi2Te3) are prepared by thermal evaporation from nanopowders on the glass substrates. The XRD patterns of films show that all the films are polycrystalline and the crystalline increased by annealing temperature. Measuring of the thermoelectric power of thin films in the temperature range 300 to 380 K shows that Seebeck Coefficients have both negative and positive values, indicating that the films have both n-type and p-type conductivity. The re-crystallization of films is done by annealing from 130°C to 175°C and Seebeck Coefficient varied from -150 to 100 μV/K.

Effect of Substructure on the Thermoelectric Power of aβ-Quenched ZrCrFe Alloy

β-quenching a Zr-1.15 wt％Cr-0.10 wt％Fe alloy produces a martensitic or a Widmanst(a|¨)tten transforma- tion morphology,or a mixture of the two,depending on the cooling rate.For the Widmanst(a|¨)tten structure,or the mixed martensitic-Widmanst(a|¨)itten structure,a grain boundary phase is observed at most prior-β grain boundaries.X-ray line broadening analysis and the thermoelectric power(TEP)measurements of these quenched samples show that not only the solubility of alloying elements in α-Zr matrix,but also substructure (microstrain,crystallite size and dislocation density)have an effect on TEP.Thus,TEP measurements are very well suited for following the structural transformations taking place in Zr alloys during fabrication.

THERMOELECTRIC POWER OF Y_(0.6)Ba_(0.4)CuO_(3-x)

The thermoelectric power of the high-temperature super-conductor Y_(0.6)Ba_(0.4)CuO_(3-x) was measured as a function of temperature between 77-300K.A change in sign of thermoelectric power was observed around 205K.This indicates that the charge carriers are predominantly electrons at temperatures above 205K and positive carriers below 205K.till the temperature reaches that corresponding to zero thermoelectric power.

Thermoelectric interface materials:A perspective to the challenge of thermoelectric power generation module

The past years has observed a significantly boost of the thermoelectric materials in the scale of thermoelectric figure-of-merit,i.e.ZT,because of its promising application to harvest the widely distributed waste heat.However,the simplified thermoelectric materials'performance scale also shifted the focus of thermoelectric energy conversion technique from devices-related efforts to materials-level works.As a result,the thermoelectric devices-related works didn't get enough attention.The device-level challenges behind were kept unknown until recent years.However,besides the thermoelectric materials properties,the practical energy conversion efficiency and service life of thermoelectric device is highly determined by assembling process and the contact interface.In this perspective,we are trying to shine some light on the device-level challenge,and give a special focus on the thermoelectric interface materials(TEiM)between the thermoelectric elements and electrode,which is also known as the metallization layer or solder barrier layer.We will go through the technique concerns that determine the scope of the TEiM,including bonding strength,interfacial resistance and stability.Some general working principles are summarized before the discussion of some typical examples of searching proper TEiM for a given thermoelectric conversion material.

Role of phonon drag and carrier diffusion in thermoelectric power of polycrystalline La_(0.97)Na_(0.03)MnO_(3)manganites

We develop a theoretical model for quantitative analysis of temperature-dependent thermoelectric power of monovalent(Na)doped La_(0.97)Na_(0.03)MnO_(3)manganites.In the ferromagnetic regime,we have evaluated the phonon thermoelectric power by incorporating the scattering of phonons with impurities,grain boundaries,charge carriers and phonons.In doing so,we use the Mott expression to compute the carrier(hole)diffusion thermoelectric power(S_(c)^(diff))using Fermi energy as carrier(hole)-free parameter,and S_(c)^(diff)shows linear temperature dependence and phonon drag S_(ph)^(drag)increases exponentially with temperature which is an artifact of various operating scattering mechanisms.It is also shown that for phonons the scattering and transport cross-sections are proportional toω^(4)in the Rayleigh regime wherewis the frequency of the phonons.Numerical analysis of thermoelectric power from the present model shows similar results as those revealed from experiments.

Preparation and thermoelectric properties of ternary rare earth sulfide γ-Ce_(3–x)Eu_xS_4

The effect of Eu-substitution on the density and thermoelectric properties of ternary sulfide Ce3-xEuxS4 （0≤x≤0.8） compacts was investigated. Ce3-xEuxS4 powders were prepared via the sulfurization of the oxide using CS2 gas at 1473 K. The pressureless sintered Ce3-xEuxS4 compacts in the atmosphere were crystallized in the T-phase. The density of the Ce3-xEuxS4 compacts increased with the increasing of Eu-substitution. Eu-substitution yielded a higher Seebeck coefficient and lower electrical resistivity. The highest value of the thermoelectric power factor of 1.41×10^-4 W/K^2m was obtained for the Ce2.2Eu0.8S4 compact at 673 K. It indicated that Eu-substitution was effective for improving thermoelectric properties of Ce3-xEuxS4.

Quantum phase transitions in CePdAl probed by ultrasonic and thermoelectric measurements

CePdAl has been recently recognized as a frustrated antiferromagnetic heavy-fermion compound with a pressureor field-tuned,extended quantum critical phase at zero temperature.Identifying characteristic signatures of the emerging quantum critical phase,which are expected to be distinct from those near a quantum critical point,remains challenging.In this work,by performing ultrasonic and thermoelectric measurements down to very low temperatures in a^(3)He–^(4)He dilution refrigerator in the presence of magnetic field,we are able to obtain some crucial thermodynamic and thermal transport features of the quantum critical phase,including a frustration-related elastic softening detected by ultrasound and a Fermi-surface change probed by thermoelectric effect.

Location of Large-Scale Concentrating Solar Power Plants in Northeast Brazil

Heliothermic electricity generation is gaining popularity in several countries worldwide. In Brazil, this form of energy generation has not yet been explored for large scale projects. However, the country possesses extensive areas with normal and high-intensity direct irradiation and low seasonality factors, particularly in the semi-arid region of the Brazilian Northeast. The region also presents other important features for setting up such plants: proximity to transmission lines, sufficient flatness, non-endangered vegetation, a suitable land use profile low maximum wind speeds, low population density, and more recently, an increase in the demand for local electric energy due to economic growth above the Brazilian average. A Geographic Information System includes a set of specialised resources that allow us to manipulate spatial data, providing quickness and efficiency in the identification of appropriate places for installing solar power plants while also preparing us for future scenarios, with regards to their impacts, costs and benefits. This article presents a study of the optimal location for thermoelectric power plants in the semi-arid region of the Brazilian Northeast on the scale of 1:10,000,000. All provinces with good potential for the implementation of large-scale concentrating solar power plants are identified. Considering that the installed capacity for parabolic cylindrical concentrators in terrains with a steepness of less than 1% is 43.26 MW/km2 for systems without storage and 30.82 MW/km2 for systems with 6 hours of storage, the potential of the southeast region of Piauí alone is huge. Even with the lack of information about the urban areas, terrain continuity, and other variables,utilising only 10% of the identified potential area, or879.7 km2, would result in an installed capacity of 38.1-27.1 GW. This value corresponds to more than 1/3 of the potency of the current Brazilian electric system. If the same calculation is made for the semi-arid region of the Brazilian Northeast, its capacity will be greater than 1000 GW.

Influence of Structure Parameters on Performance of the Thermoelectric Module

A numerical model of thermoelectric module （TEM） is created by academic analysis,and the impacts of the resistance ratio and thermoelement size on the output power and thermoelectric efficiency of the TEM are analyzed by the MATLAB numerical calculation.The numerical model is validated by the ANSYS thermal,electrical,and structural coupling simulation.The effects of the variable physical property parameters and contact effect on the output power and thermoelectric efficiency are evaluated,and the concept of aspect ratio optimal domain is proposed,which provides a new design approach for the TEM.

Cascade utilization of full spectrum solar energy for achieving simultaneous hydrogen production and all-day thermoelectric conversion

Solar-driven photocatalytic water/seawater splitting holds great potential for green hydrogen production.However,the practical application is hindered by the relatively low conversion efficiency resulting from the inadequate utilization of solar spectrum with significant waste in the form of heat.Moreover,current equipment struggles to maintain all-day operation subjected to the lack of light during nighttime.Herein,a novel hybrid system integrating photothermal catalytic(PTC)reactor,thermoelectric generator(TEG),and phase change materials(PCM)was proposed and designed(named as PTC-TEG-PCM)to address these challenges and enable simultaneous overall seawater splitting and 24-hour power generation.The PTC system effectively maintains in an optimal temperature range to maximize photothermal-assisted photocatalytic hydrogen production.The TEG component recycles the low-grade waste heat for power generation,complementing the shortcoming of photocatalytic conversion and achieving cascade utilization of full-spectrum solar energy.Furthermore,exceptional thermal storage capability of PCM allow for the conversion of released heat into electricity during nighttime,contributing significantly to the overall power output and enabling PTC-TEG-PCM to operate for more than 12 h under the actual condition.Compared to traditional PTC system,the overall energy conversion efficiency of the PTC-TEG-PCM system can be increased by∼500%,while maintaining the solar-to-hydrogen efficiency.The advancement of this novel system demonstrated that recycling waste heat from the PTC system and utilizing heat absorption/release capability of PCM for thermoelectric application are effective strategies to improve solar energy conversion.With flexible parameter designing,PTC-TEG-PCM can be applied in various scenarios,offering high efficiency,stability,and sustainability.

Transport Properties of Bi_2S_3 Single Crystals

Bi2S3 single crystals were grown by using a modification of Bridgman method. Measurements of the electrical conductivity, Hall effect and thermoelectric power （TEP） were preformed in two crystallographic directions （parallel and perpendicular to the c-axis）. The measurements showed that the electrical conductivity, Hall mobility, and Seebeck coefficient have anisotropic nature. From these measurements some physical parameters were estimated and the crystals showed n-type of conduction mechanism. Also, values of the energy gap were found to be different in the two directions.

Kinetic Study of Phase Transformations in Zr-Cr-Fe Alloy

The effect of prior microstructure on the kinetics of the α- β phase transformation in Zr-1.14 wt%Cr 0.08 wt%Fe alloy was studied. Specimens of different metallurgical histories and hence microstructures were prepared. Thermoelectric power (TEP) measurements and optical metallographt wereused to examine the transformations produced in these three kinds of specimens when they were reheated totemperatures 800～100℃ at different heating rates (slow and fast). The results indicate that the kinetics ofthe α-βphase transformation is strongly influenced by the metallurgical history of specimens. The presenceof nonequilibnum structures accelerates the phase transformation in the alloy and decreases the x-β transfor-mation temperature from 950℃ to 870℃. The influence of experimental conditions on the transformationkinetics is more complicated than that of metallurgical history. For an heated and as-received specimens, theα-βtransformation kinetics of the fast-heated specimens is slower than for the slow-heated specimens. How-ever. in the quenched specimens, the transformation kinetics of slow-heated specimens is greater than in fastheated specimens. This behaviour may be related to the size and shape of the Zr(CrFe)_2 precipitates andthe homogenization of the matrix.

Zn_4Sb_3高性能热电材料的制备(英文)

A "reaction-extrusion process" has been developed to prepare Zn4Sb3 bulk materials with high thermoelectric performance.The synthesis,densification,and shape-forming of Zn4Sb3 bulk materials were realized simultaneously in one hot-extrusion process,and the resulting extrudates had high density with single β-Zn4Sb3 phase.A large extrusion ratio and a small punch speed are advantageous to enhance thermoelectric performance.The extruded Zn4Sb3 materials exhibited excellent thermoelectric performance,for example,the dimensionless thermoelectric figure of merit is 1.77 at 623 K,which is 36% higher compared to conventional hot-pressed materials.On the other hand,the incorporation of 1% SiC nanosized particles into Zn4Sb3 matrix leads to improvements in both thermoelectric and mechanical properties.

Fabrication and thermoelectric properties of Yb-doped ZrNiSn half-Heusler alloys

Half-Heusler(HH)alloys constitute an important class of materials that exhibit promising potential in high-temperature thermoelectric(TE)power generation.In this work,we synthesized Zr_(1−x)Yb_(x)NiSn(x=0,0.01,0.02,0.04,0.06 and 0.10)HH alloys using a time-efficient levitation melting and spark plasma sintering procedure.X-ray diffraction showed that the samples were predominantly single phased,and that the lattice constant increased systematically with increasing Yb doping ratio.The doping effects of Yb on the thermoelectric properties were studied.It was found that Yb doping consistently decreased the electrical and thermal conductivities.On the other hand,the effects of Yb doping on the Seebeck coefficient were found to be non-monotonic.The magnitude of the Seebeck coefficient(n-type)was increased upon Yb doping up to x=0.02,above which Yb doping introduced notable p-type conduction.As a result,the room-temperature Seebeck coefficient of the x=0.10 sample became positive although the magnitude was not high.The thermoelectric figure of merit,ZT,reached a maximum of∼0.38 at 900 K for the x=0.01 sample.Selective doping on the Ni and Sn sites are necessary to further optimize the TE performance of Zr_(1−x)Yb_(x)NiSn alloys.

Wide spectrum solar energy harvesting through an integrated photovoltaic and thermoelectric system

This paper proposes a power system concept that integrates photovoltaic （PV） and thermoelectric （TE） technologies to harvest solar energy from a wide spectral range. By introduction of the ＇spectrum beam splitting＇ technique, short wavelength solar radiation is converted directly into electricity in the PV cells, while the long wavelength segment of the spectrum is used to produce moderate to high temperature thermal energy, which then generates electricity in the TE device. To overcome the intermittent nature of solar radiation, the system is also coupled to a thermal energy storage unit. A systematic analysis of the integrated system is carried out, encompassing the system configuration, material properties, thermal management, and energy storage aspects. We have also attempted to optimize the integrated system. The results indicate that the system configuration and optimization are the most important factors for high overall efficiency.

Thermoelectric properties of Yb x Co_4 Sb_(12) system

Yb x Co 4 Sb 12 polycrystals were fabricated by vacuum melting combined with hot-press sintering.The effect of Yb-filling on thermoelectric property of unfilled skutterudite CoSb 3 was investigated,which indicated the enhancement of the power factor of the material.Transport properties of materials changed from semi-conductor to semi-metal during the measurement of electrical conductivity,which indicated the change of electronic band structure.The maximum value of electrical conductivity was about 190000 S/m at 300 K for all samples.On the basis of Yb-filling,power factor of Yb 0.2 Co 4 Sb 12 reached 5-6 mW/（m·K） during the measurement temperature.Thermal conductivity decreased with increase of Yb content,and the thermal conductivity of Yb 0.2 Co 4 Sb 12 reached 3.2 W/（m·K） at 600 K.The ZT value of Yb 0.2 Co 4 Sb 12 reached 1.16 at 700 K due to positive contribution from high power factor and low thermal conductivity.

Photothermal hygroscopic hydrogel for simultaneous generation of clean water and electricity

Harvesting water from the air using adsorbents and obtaining fresh water by solar-driven desorption is considered as one of the most effective ways to solve the freshwater crisis in arid and desert regions.Based on a simple and low-cost photothermal hygroscopic hydrogel,a new strategy is proposed to boost solar energy efficiency by coupling solar-driven atmospheric water harvesting technology with thermoelectric power generation technology in this paper.Photothermal hygroscopic hydrogel ink PAM-CaCl_(2)is prepared by in situ polymerization using Acrylamide as monomer,Ammonium persulfate as thermal initiator and CaCl_(2)as hygroscopic component.During the day,the photothermal hygroscopic hydrogel absorbs solar energy and evaporates its own internal water to obtain fresh water.Simultaneously,the residual waste heat is utilized to power the thermoelectric panel,which produces electricity based on Seebeck effect.At night,the hydrogel harvests water molecules in the air to achieve regeneration.This hybrid system can achieve a water production rate of 0.33 kg m^(-2)h^(-1)and an additional electrical energy gain of 124 mW m^(-2)at 1 kW m^(-2)solar intensity.Theoretical model of the hybrid system is developed to understand the heat flow and thermoelectric generation process.The results provide new insights into energy and freshwater replenishment options in arid or desert areas with abundant solar energy.

Development of Kabila rocket: A radioisotope heated thermionic plasma rocket engine

A new type of plasma rocket engine, the Kabila rocket, using a radioisotope heated thermionic heating chamber instead of a conventional combustion chamber or catalyst bed is intro- duced and it achieves specific impulses similar to the ones of conventional solid and bipropellant rockets. Curium-244 is chosen as a radioisotope heat source and a thermal reductive layer is also used to obtain precise thermionic emissions. The self-sufficiency principle is applied by simultane- ously heating up the emitting material with the radioisotope decay heat and by powering the differ- ent valves of the plasma rocket engine with the same radioisotope decay heat using a radioisotope thermoelectric generator. This rocket engine is then benchmarked against a 1 N hydrazine thruster configuration operated on one of the Pleiades-HR-1 constellation spacecraft. A maximal specific impulse and power saving of respectively 529 s and 32% are achieved with helium as propellant. Its advantages are its power saving capability, high specific impulses and simultaneous ease of storage and restart. It can however be extremely voluminous and potentially hazardous. The Kabila rocket is found to bring great benefits to the existing spacecraft and further research should optimize its geometric characteristics and investigate the physical principals of its operation.

Optical and electrical properties and phonon drag effect in low temperature TEP measurements of AgSbSe_2 thin films

Polycrystalline thin films of silver antimony selenide have been deposited using a reactive evaporation technique onto an ultrasonically cleaned glass substrate at a vacuum of 10-5 torr. The preparative parameters, like substrate temperature and incident fluxes, have been properly controlled in order to get stoichiometric, good quality and reproducible thin film samples. The samples are characterized by XRD, SEM, AFM and a UV-vis-NIR spectrophotometer. The prepared sample is found to be polycrystalline in nature. From the XRD pattern, the average particle size and lattice constant are calculated. The dislocation density, strain and number of crystallites per unit area are evaluated using the average particle size. The dependence of the electrical conductivity on the temperature has also been studied and the prepared AgSbSe2 samples are semiconducting in nature. The AgSbSe2 thin films exhibited an indirect allowed optical transition with a band gap of 0.64 eV. The compound exhibits promising thermoelectric properties, a large Seebeck coefficient of 30 mV/K at 48 K due to strong phonon electron interaction. It shows a strong temperature dependence on thermoelectric properties, including the inversion of a dominant carrier type from p to n over a low temperature range 9-300 K, which is explained on the basis of a phonon drag effect.