Papers by Keyword: Seebeck Coefficient

Abstract: This paper investigates computationally the performance of a commercially available Seebeck module under open circuit conditions. Seebeck modules, also called thermoelectric generators, are solid state devices used for power generation purposes. One of the most attractive applications of these devices is the exploitation of waste heat vastly available through various environmental or industrial sources. A Seebeck module can be used as a stand-alone device or as a part of a bigger power generation system. Device computational modeling has been performed using ANSYS Workbench (v. 14.0).

Abstract: In this work, we report the preparation of transition metal deposited flexible multiwalled carbon nanotube buckypaper for thermoelectric applications. MWCNT buckypaper prepared by dispersion and filtration method was then deposited with the transition metals such as silver (Ag) and copper (Cu) by the electrodeposition method. We measured the voltage yield of Ag and Cu-doped buckypaper by making the temperature gradient along the sample. We established the temperature dependent Seebeck coefficient for Ag and Cu-doped buckypaper and found significant increase in the S(T). It is also revealed that remarkable rise in the value of S(T) and output voltage by connecting 3-sheets of BP in series. Here we determined the enhancement of Seebeck coefficient by increasing the number of BP sheets, thereby improving the thermoelectric efficiency. Furthermore, these paper-like CNT films show good flexibility, which makes them possible to be widely applied in various flexible energy conversion devices.

Abstract: The authors examined the thermal and electrical transport properties of Tl₇Sb₂ at temperatures ranging from room temperature to 400 K. The crystal system of Tl₇Sb₂ is cubic with the lattice parameter a = 1.16053 nm and the space group is Im3m. The polycrystalline samples were prepared by melting stoichiometric amounts of thallium and antimony. Although, usually the thermal conductivity of thallium compounds is very low (<1 Wm^-1K^-1), that of Tl₇Sb₂ was relatively high (~13 Wm^-1K^-1 at room temperature). This is because of the large electronic contribution to the thermal conductivity.

Abstract: The polycrystalline Zn-doped CuAlO₂ ceramics were obtained by solid state reaction method. The mixture of high purity grade of CuO, Al₂O₃ and Zn (CH₃COO)₂2H₂O powders was ground and then pressed by using uniaxial pressure. The obtained pellet was sintered in air at 1,150 °C for 24 h. XRD patterns showed the crystal structure of the as-sintered CuAl_1-xZn_xO₂ (0x0.05) belonging to rhombohedral, space groupalong with the CuO and CuAl₂O₄ phases. From SEM micrographs, the grain size slightly decreases when the amount of Zn in CuAl_1-xZn_xO₂ samples increases. Hall mobility and hole concentration of the as-sintered samples were obtained from Hall effect measurements in van der Pauw configuration at room temperature. The electrical resistivity measurements as a function of temperature were performed. The variation of Seebeck coefficient and power factor as a function of temperature was also investigated. In the present study, the Zn-doped CuAlO₂ ceramics probably have advantages for use in high temperature thermoelectric devices.

Abstract: We describe the development of apparatus for measuring of electrical conductivity and Seebeck coefficient with high precision from 85 K to 1,200 K. Electrical resistance was measured by means of four-point probe method as a function of temperature. The temperature below 400 K was measured by using type T thermocouple in vacuum system was used and from 400 to 1,200 was measured by using Type S was applied for temperature between 400 and 1200 Kelvin in an inert gas system. With the dimensions of the specimen, the electrical resistivity (ρ_T) can be obtained in the unit of microohm-centimeter (μΩ-cm) and be written in polynomial, ρT=-0.3191+6.8×10-3T-6.0×10-7 T2+8.0×10-10T3. The electrical conductivity can be obtained by taking inversion of the electrical resistivity. Seebeck coefficient (α_T ) can be calculated in microvolt per Kelvin as follows: αT=1.9653-1.49×10-2T+9.0×10-5T2-2.0×10-7T3+2.0×10-10T4-1.0×10-13T5+3.0×10-17T6 , when T is temperature in K. The Seebeck coefficient data was compared with X-ray diffraction (XRD) and X-ray fluorescence (XRF) of the specimen. The result showed that our developrd apparatus yields the same as standard method when copper with purity greater than 99 percent was employed.

Abstract: we proposed a scheme for simulating the electronic and thermoelectric properties of polycrystalline ceramics. The simulation results show that the ground state electrons are easily confined in the largest grain. In addition, with the increasing average grain size, the Seebeck coefficient decreases while the electrical conductivity increases monotonically. The simulation results agree well with the available experimental results. Therefore, the proposed model is proved to be a promising approach for thermoelectric investigations.

Abstract: The thermoelectric phenomenon can be used for a wide application spectrum. Typically, the Seebeck effect of metallic materials is used for temperature measurement in common thermocouples. However, there is also a high potential for adapting the effect in nondestructive testing due to a high sensitivity of the thermoelectric properties to a variety of material characteristics.Different studies point out an influence of plastic deformations on the thermoelectric behavior of metals, but a detailed and quantitative analysis and description is not provided yet. There is an increasing interest in detecting the changes of properties by nondestructive characterization of plastically deformed materials. Especially in metal forming, the knowledge about the correlation between the degree of deformation and the thermoelectric behavior can help to check formed metal parts. On that account, the influence of plastic deformations on the thermoelectric behavior, in particular the Seebeck coefficient, of four steel alloys is introduced in this paper.An apparatus based on the integral measuring method was built up to measure the relative Seebeck coefficient to a reference material at different temperature gradients and for several degrees of plastic deformation. Well defined values of plastic deformation are realized by cold rolling. With this compressive forming technology a logarithmic deformation φ up to 2.11 was set for all steel alloys. Besides a high degree of deformation, a uniform strain over the sample thickness can be obtained by rolling.With increasing plastic deformation a significant change of the relative Seebeck coefficient can be observed in a defined temperature range for all investigated steels. The plastic deformation is accompanied by an increase of dislocation density into the lattice structure of the metal. These line defects provoke the formation of new scattering centers and thus the electron motion is disturbed. By the combination of metallurgical examinations and measurements of micro hardness, the relation between the thermoelectric behavior and the plastic deformation of steels can be clearly illustrated.

Abstract: The studies on the thermoelectric (TE) properties of 3,4,9,10-Perylenetetracarboxylic dianhydride (PTCDA) and a conducting polymer Poly(ethylenedioxythiopene): poly(styrenesulfonate) (PEDOT:PSS)–PH1000 are presented. PTCDA and PEDOT:PSS have been used as a potential n-type material and a p-type material for the TE device, respectively. The Seebeck coefficients, open circuit voltage and the output power have been obtained for the fabricated TE device. The Seebeck effect was observed on this TE device where the output power in the range of 1 nW/cm2 to 5 nW/cm2,was successfully deduced from this TE device. It was found that the association of PEDOT:PSS and PTCDA have been acting well in this TE device. However, a higher TE performance, in the future could be developed, by applying a thermal treatment and introducing a suitable dopant to this n-type material which may increase the mobility of the electrons and the Seebeck coefficient.

Abstract: Poly-crystalline Ba₈Cu₆Ag₂Si₃₈ clathrates were synthesized by the arc-melting method and a subsequent annealing treatment. The main phase of all the samples was type-I clathrate. However, there were some precipitates which rich in Cu, Ag or Si in the grain boundary of the as-synthesized sample and the precipitates gradually reduced with the increase of annealing time. The transition metal content in the clathrate increased with the annealing time because of the diffusion of the Cu and Ag atoms from precipitates phase into clathrates phase. The as-synthesized sample was n-type material. For the 576 hours annealed sample, the carrier type changed from n-type to p-type because of the increase of Cu and Ag content in the clathrate.

Abstract: FeSb₂ was recently found to be a narrow-gap semiconductor with strong electronelectron correlation and a large thermopower at low temperatures. We report measurements of the electrical resistivity, Seebeck coefficient and thermal conductivity between 5 K to 300 K on polycrystalline samples of FeSb₂ and FeSb_1.9. We found that the deficiency of Sb in the parent compound leads to a giant anomalous peak in thermopower (S) at low temperatures, reaching ~ 426 μV/K at 20 K, resulting in a high thermoelectric power factor at low temperatures, achieving 10 μW/K²m at 27 K._. Consequently, a significantly enhanced thermoelectric figure of merit ZT ~ 0.0015 is achieved near room temperature. At low temperatures there is no improvement in ZT values due to the high thermal conductivity (phonon dominant region). Keywords: Seebeck coefficient, thermal conductivity, resistivity, thermoelectric figure of merit. PACS: 72.20.Pa, 71.27.+a, 71.28.+d