Effect of metal electrode on thermoelectric power in bismuth telluride compounds

摘要

The measurements of apparent effective Seebeck coefficients S a, thermoelectric powers ΔE and I-V characteristics were made on a copper-semiconductor-metal contact junction, where the semiconductor is consisted of the p- and n-type bismuth telluride compounds. The S a measured by heating either of copper and metal alternatively to produce the temperature differences of ΔT = ±6 K changed slightly with the kind of metal electrodes, but it changed very little when the direction of the temperature gradient was reversed. The averaged 〈S a〉 values over all kinds of metal electrodes agreed closely with the Seebeck coefficients S measured by the conventional technique using two alumel-chromel thermocouples as an electrode. The thermoelectric power ΔE generated by imposing the temperature differences of ΔT = ±6 K on a thermoelement tended to increase with increase of S a and reached large values in noble metal electrodes of Ag and Au. The ΔE was found to achieve enhancements of up to 10% or even more, when one end of a thermoelement contacts with Au electrode and the external electrical resistance is zero. Thus, the selection of the optimal metal electrode is necessary to make the thermoelectric conversion efficiency as high as possible.