Reference Material for Seebeck Coefficients

Abstract

This paper describes a measurement method and a measuring system to determine absolute Seebeck coefficients of thermoelectric bulk materials with the aim of establishing reference materials for Seebeck coefficients. Reference materials with known thermoelectric properties are essential to allow a reliable benchmarking of different thermoelectric materials for application in thermoelectric generators to convert thermal into electrical energy or vice versa. A temperature gradient (1 to 8) K is induced across the sample, and the resulting voltage is measured by using two differential Au/Pt thermocouples. On the basis of the known absolute Seebeck coefficients of Au and Pt, the unknown Seebeck coefficient of the sample is calculated. The measurements are performed in inert atmospheres (N 2 ) and at low pressure (30 to 60) mbar in the temperature range between 300 K and 860 K. The measurement results of the Seebeck coefficients of metallic and semiconducting samples are presented. Achievable relative measurement uncertainties of the Seebeck coefficient are on the order of a few percent.

Analysis of the “cold finger effect” in measuring the Seebeck coefficient

“…For comparison, the reference values of ISOTAN ® are also presented in the last column. The measurement uncertainty of these reference values is 3.2 µV K −1 for (k = 2) [14], which is also considered as the uncertainty of the measured values of S in this work.…”

From surface data to bulk properties: a case study for antiphase boundaries in GaP on Si(001)

“…The structural findings for the APDs imply a possible application: Thermoelectric materials with a high and reproducible quality factor are the focus of current research [26,53,54]. As thermoelectric materials rely on a temperature gradient to be sustained within them, their quality factor is inversely proportional to the thermal conductivity of the material.…”

Entwicklung von zertifizierten Referenzproben für den thermoelektrischen Leistungsfaktor

“…Die Grundlage der Bewertung von thermoelektrischen Referenzproben ist die präzise und rückführbare Messung der thermoelektrischen Transporteigenschaften Seebeck-Koeffizient (S), elektrische Leitfähigkeit (σ), und Wärmeleitfähigkeit (κ). Für die Zertifizierung von thermoelektrischen Referenzmaterialien für den Seebeck-Koeffizienten wurde bisher an der PTB das IPM-SRX-Messsystem eingesetzt [1] was vom Fraunhofer Institut für Physikalische Messtechnik (IPM) entwickelt wurde. Mit diesem Messsystem kann der Seebeck-Koeffizient im Temperaturbereich zwischen 300 K und 860 K genau gemessen werden, die Genauigkeit der Messung der elektrischen Leitfähigkeit ist jedoch begrenzt.…”

“…Die Überprüfung der Messgenauigkeit der SRX-Anlage bezüglich des Seebeck-Koeffizienten erfolgte durch Messungen an drei zufällig ausgewählten Proben des bekannten Referenzmaterials für Seebeck-Koeffizienten RN/SB-ISOTAN-01 [1]. Die Ergebnisse sind in Abbildung 7 dargestellt.…”

“…The development of efficient thermoelectric materials and TEGs suffer from the lack of suitable reference materials and traceable measurement technology. Therefore, the Physikalisch-Technische Bundesanstalt (PTB) has been developing thermoelectric reference materials and the associated measurement technology for several years [1]. The current "TEST-HT" project (Thermoelektrische Standardisation für hohe Temperaturen) has the objective to develop the first semiconducting reference material for the power factor in the range from 300 K to 1000 K. The material selected was cobalt-doped β-iron disilicide (β-Fe0.95Co0.05Si2) (FeSi2), which is manufactured by our project partner, the German Aerospace Center (DLR) [2].…”