Thermoelectric Measurements at Small-Area Contacts

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Abstract
The measurement of the effects of heating a substance in the vicinity of a metal contact by means of an electrical current leads to the determination of various combinations of the thermoelectric parameters sufficient to determine the electrical conductivity, the thermal conductivity, and the Seebeck coefficient. If the metal contact is small, radiation causes negligible error in the determination of the thermal conductivity. One of the combinations obtained directly is the thermoelectric figure of merit. Equations are derived which relate to the heating current an observed thermoelectric voltage or change in resistance caused by a change in temperature at a small area contact. Geometric factors are found to cancel out of these equations. Quantitative relations are also presented which set limits on the effects of radiation. An experimental method is described which has been used for making such measurements, and some experimental results are reported which permit comparison to conventional measurements in accuracy. Ways in which measurements of thermal diffusivity can be combined with the other measurements are also discussed.