Comments on “The Effects of Gaseous Helium and Nitrogen on Thermopower   Measurements: A Note of Concern for the Discrepancy of the Results   Observed in High Temperature Superconductors”

Villaflor, A.B.; Luna, Luis H. de

doi:10.1143/jjap.33.4051

Cited by 4 publications

(1 citation statement)

References 2 publications

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“…For example, many commercial apparatus require back filling of helium gas between 25 and 30 kPa (≈200 Torr) to achieve reliable thermal contact. There are reports suggesting low pressure gases such as helium and nitrogen may affect the measured Seebeck coefficient value [15,22,23]. The presence of high thermal conductivity gases will introduce additional parasitic heat losses and consequently error in the Seebeck coefficient.…”

Section: Identifying Error Arising From Nonisothermal Contactmentioning

confidence: 99%

Protocols for the high temperature measurement of the Seebeck coefficient in thermoelectric materials

Martin¹

2013

Meas. Sci. Technol.

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In Seebeck coefficient metrology, the present diversity in apparatus design, acquisition methodology and contact geometry has resulted in conflicting materials data that complicate the interlaboratory confirmation of reported high efficiency thermoelectric materials. To elucidate the influence of these factors in the measurement of the Seebeck coefficient at high temperature and to identify optimal metrology protocols, we measure the Seebeck coefficient as a function of contact geometry under both steady-state and transient thermal conditions of the differential method, using a custom developed apparatus capable of in situ comparative measurement. The thermal gradient formation and data acquisition methodology, under ideal conditions, have little effect on the measured Seebeck coefficient value. However, the off-axis 4-probe contact geometry, as compared to the 2-probe, results in a greater local temperature measurement error that increases with temperature. For surface temperature measurement, the dominant thermal errors arise from a parasitic heat flux that is dependent on the temperature difference between the sample and the external thermal environment, and on the various thermal resistances. Due to higher macroconstriction and contact resistance in the 4-probe arrangement, the measurement of surface temperature for this contact geometry exhibits greater error, thereby overestimating the Seebeck coefficient.

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Section: Identifying Error Arising From Nonisothermal Contactmentioning

confidence: 99%

Protocols for the high temperature measurement of the Seebeck coefficient in thermoelectric materials

Martin¹

2013

Meas. Sci. Technol.

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High temperature Seebeck coefficient metrology

Martin

Tritt

Uher

2010

Journal of Applied Physics

199

154

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We present an overview of the challenges and practices of thermoelectric metrology on bulk materials at high temperature (300 to 1300 K). The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential property measurement for evaluating the potential performance of novel thermoelectric materials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at high temperature. This has led to the implementation of nonideal practices that have further complicated the confirmation of reported high ZT materials. To ensure meaningful interlaboratory comparison of data, thermoelectric measurements must be reliable, accurate, and consistent. This article will summarize and compare the relevant measurement techniques and apparatus designs required to effectively manage uncertainty, while also providing a reference resource of previous advances in high temperature thermoelectric metrology.

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Apparatus for the high temperature measurement of the Seebeck coefficient in thermoelectric materials

Martin

2012

Review of Scientific Instruments

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The Seebeck coefficient is a physical parameter routinely measured to identify the potential thermoelectric performance of a material. However, researchers employ a variety of techniques, conditions, and probe arrangements to measure the Seebeck coefficient, resulting in conflicting materials data. To compare and evaluate these methodologies, and to identify optimal Seebeck coefficient measurement protocols, we have developed an improved experimental apparatus to measure the Seebeck coefficient under multiple conditions and probe arrangements (300 K-1200 K). This paper will describe in detail the apparatus design and instrumentation, including a discussion of its capabilities and accuracy as measured through representative diagnostics. In addition, this paper will emphasize the techniques required to effectively manage uncertainty in high temperature Seebeck coefficient measurements.

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Comments on “The Effects of Gaseous Helium and Nitrogen on Thermopower Measurements: A Note of Concern for the Discrepancy of the Results Observed in High Temperature Superconductors”

Cited by 4 publications

References 2 publications

Protocols for the high temperature measurement of the Seebeck coefficient in thermoelectric materials

Protocols for the high temperature measurement of the Seebeck coefficient in thermoelectric materials

High temperature Seebeck coefficient metrology

Apparatus for the high temperature measurement of the Seebeck coefficient in thermoelectric materials

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