MEASUREMENTS OF THE SEEBECK COEFFICIENT OF THERMOELECTRIC-MATERIALS BY AN AC METHOD

An ac method for measurement of the Seebeck coefficient was developed. Specimens were heated periodically at frequencies in the range 0.2-10 Hz using a semiconductor laser. The small temperature increase and th e resultant thermoelectric power were measured with a Pt-Pt 13% Rh the rmocouple (25 mu m in diameter) through a lock-in amplifier. The Seebe ck coefficient of a Pt90Rh10 foil measured by the ac method was in agr eement with that obtained from the standard table. The optimum frequen cy and specimen thickness for the ac method were 0.2 Hz and 0.1-0.2 mm , respectively. The Seebeck coefficients of silicon single crystal and several thermoelectric semiconductors (Si80Ge20, PbTe, FeSi2, SiB14) measured by the ac method agreed with those measured by a conventional de method in the temperature range between room temperature and 1200 K. The time needed for each measurement was less than a few tens of mi nutes, significantly shorter than that for a conventional dc method.