Simultaneous measurement of the Seebeck coefficient and thermal diffusivity for bulk thermoelectric materials

Homma, Ryoei; Hasegawa, Yasuhiro; Terakado, Hiroki; Morita, Hiroyuki; Komine, Takashi

doi:10.7567/jjap.54.026602

Cited by 11 publications

(12 citation statements)

References 18 publications

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“…3 shows the temperature dependence of the assumed Seebeck coefficient from 25 K to 300 K from previous work as a conditional value. 14,20 By the definition of zT, it also shows the estimated temperature dependence of the thermal conductivity for the module (κ = S 2 ρzT T ). At 300 K, the estimated thermal conductivity was ∼1.90 W/mK, which is reasonable compared to that for the NIST Bi 2 Te 3 sample (measured to be 2.06 W/mK by the steady-state method at 300 K in a previous study).…”

Section: Resultsmentioning

confidence: 99%

Temperature dependence of dimensionless figure of merit of a thermoelectric module estimated by impedance spectroscopy

Hasegawa

Otsuka

2018

AIP Advances

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Temperature dependence of dimensionless figure of merit zT of a Π-shaped thermoelectric module using bismuth-telluride materials was estimated on the basis of a theory of impedance spectroscopy, which is able to ascertain zT directly using only electrometric measurements from the frequency dependence of the impedance without any calorific measurement. The dependence of the module was measured from 5 mHz to 10 kHz with precise temperature control. From the analysis, the ohmic resistance, the impedance due to the Peltier effect, and the characteristic heat frequency at 300 K were determined under two different boundary conditions (the suspended and fixed conditions of a heat bath). A comparison between these boundary conditions revealed that their difference led to a slight change in the frequency dependence of the measured impedance due to the variation in the heat capacity of the module, and the estimated dimensionless figure of merit was identical for the two boundary conditions (zT ≈ 0.839 at 300 K). The temperature dependence of the dimensionless figure of merit of the module was successfully measured from 20 K to 300 K. The dependence of the thermal conductivity was also estimated with an assumed Seebeck coefficient from the definition of zT. In addition, a new method using only two impedances with repeatability was proposed and demonstrated to estimate the dimensionless figure of merit precisely (zT ≈ 0.845 at 300 K).

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Section: Resultsmentioning

confidence: 99%

Temperature dependence of dimensionless figure of merit of a thermoelectric module estimated by impedance spectroscopy

Hasegawa

Otsuka

2018

AIP Advances

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“…Thermal conductivity was derived from κ = ρ DC p , where ρ is density of the sample, and C p is heat capacity measured by differential scanning calorimetry. The thermal diffusivity was measured under a vacuum (<5 × 10 –3 Pa) by a modified Ångström method − with the same experimental configuration in the measurements of Seebeck coefficient and electrical conductivity. A sinusoidal current was supplied to the heater for creating a periodic heating wave at frequency of 0.01–0.02 Hz via Joule heating.…”

Section: Methodsmentioning

confidence: 99%

Carbon Nanoparticle Hybrid Aerogels: 3D Double-Interconnected Network Porous Microstructure, Thermoelectric, and Solvent-Removal Functions

Tan

Zhao

Gao

et al. 2017

ACS Appl. Mater. Interfaces

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We report reduced graphene oxide (rGO)/single-walled carbon nanotube (SWCNT) hybrid aerogels with enhanced thermoelectric (TE) performance and removal of organic solvents by designing 3D double-interconnected network porous microstructures. A convenient, cost-effective, and scalable preparation procedure is proposed compared with conventional high-temperature pyrolysis and supercritical drying techniques. The obtained hybrid aerogels are systematically characterized by apparent density, scanning electron microscopy, X-ray photoemission spectroscopy, Raman spectroscopy, and porosity. An enhanced TE performance of ZT ≈ ∼8.03 × 10 has been achieved due to the 3D double-interconnected network porous microstructure, the energy-filtering effect, and the phonon scattering at the abundant interfaces and joints. In addition, upon a large axial compression deformation, a high degree of retention of the Seebeck coefficient and a simultaneously significant enhancement of the electrical conductivity are observed. Finally, the hybrid aerogels display high capability for the removal of diverse organic solvents and good recyclability. These findings open a new avenue for exploiting aerogels with multifunctions and widening the applications of TE materials by judicious microstructure design.

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“…[11][12][13][14][15][16][17][18][19] We also proposed a modified Angström method of estimating the thermal diffusivity by detecting the thermoelectric voltage directly on an element without thermosensors. 20) In addition, the method has been extended to measure not only the thermal diffusivity α but also the Seebeck coefficient S, resistivity η, thermal conductivity λ, and heat capacity C, as well as the figure of merit, using an identical thermoelectric element. 21) However, this technique cannot be applied to much shorter thermoelectric elements, especially the elements in a typical module, because their usual length is less than 2 mm, and it is difficult to attach local electrodes on the side surface of elements in the module using Ag epoxy.…”

Section: Introductionmentioning

confidence: 99%

“…Here, we note that the thermal diffusivity of thermoelectric materials was predicted to be on the order of 10 −6 m 2 =s. [19][20][21] The required periodic frequency of the heat is estimated as 0.22 Hz when the length of the element is 1 mm, the phase shift angle is 10°, and a measurement point at the midpoint of the sample is used. 20) This means that the thermal diffusivity on the module can be estimated if the temperature is measured using real-time acquisition without any contact with an infrared (IR) camera in a so-called thermographic method.…”

Section: Introductionmentioning

confidence: 99%

Thermal diffusivity measurement using thermographic method and performance evaluation by impedance spectroscopy for thermoelectric module

Otsuka

Terakado

Homma

et al. 2016

Jpn. J. Appl. Phys.

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The thermal diffusivity of two bulk thermoelectric elements and a thermoelectric module was measured by an infrared camera using a thermographic method without any contact in air at room temperature. The estimated values for the elements (3.45 × 10−6 m2/s for a BiSb sample and 1.60 × 10−6 m2/s for a BiTe sample) were slightly larger than those measured in vacuum. The difference was explained as the effect of heat convection on the surface of the samples by solving the one-dimensional heat conduction equation numerically. The thermal diffusivity of thermoelectric elements in a thermoelectric module was also estimated using the thermographic method, and values of (1.1–1.7) × 10−6 m2/s in air were obtained, depending on the element. On the basis of the measurement results, the performance of the module was estimated using impedance spectroscopy, which can estimate not only the dimensionless figure of merit but also the thermal loss and response. The thermal response and thermal loss in air were similar to those in vacuum; however, the dimensionless figure of merit was 0.82 in vacuum and 0.70 in air.

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Simultaneous measurement of the Seebeck coefficient and thermal diffusivity for bulk thermoelectric materials

Cited by 11 publications

References 18 publications

Temperature dependence of dimensionless figure of merit of a thermoelectric module estimated by impedance spectroscopy

Temperature dependence of dimensionless figure of merit of a thermoelectric module estimated by impedance spectroscopy

Carbon Nanoparticle Hybrid Aerogels: 3D Double-Interconnected Network Porous Microstructure, Thermoelectric, and Solvent-Removal Functions

Thermal diffusivity measurement using thermographic method and performance evaluation by impedance spectroscopy for thermoelectric module

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