Measurements of the seebeck coefficient of thermoelectric materials by an AC method

An ac method Ior measurement of the Seebeck coefl]cient was developed. Specimens were heated periodically at frequencies in the range 0.2 l0 Hz using a semiconductor laser. The small teml~erature increase and the resultant thermoelectric power were measured with a Pt PI 13 % Rh thernaocouple (25 itm in diameter) through a lock-in amplifier. The Seebeck coetllcient of a Pt,. Rh u. foil measured by the ac method was in agreement with that obtained from the standard table. The optimum frequency and specimen thickness Ibr the ac method were 0.2 ]];,: and [).[ 0.2 nlnl, respectively. The Seebeck coellicicnts of silicon single crystal and several thermoelectric semiconductors [Si~.Ge_,,,. PbTc. VeSi_,. SiBul measured by the ar method agreed with those measured by tl r dg Ille[hod in the tenlperature range between roonl [gnlpelaturc and 1200 K. The time needed Ibr each measurement was less than a few tens of minutes, significantly shorter than daat lbr a conventional dc method.