Annealing effect on thermoelectric performance for hot-press sintered chromium disilicide (CrSi/sub 2/)

Abstract

The effect of annealing process on thermoelectric properties has been researched for hot-press sintered chromium disilicide (CrSi/sub 2/) in order to enhance the thermoelectric performance. Annealing period under the proper annealing temperature was found to affect the transport properties such as carrier concentration, Hall mobility and scattering mechanisms, so that the thermoelectric properties such as the Seebeck coefficient and electrical conductivity were dependent on the annealing period. The experiments have been carried out for 0.9 atm% Ag-doped chromium disilicide produced by the hot-press sintering process varying annealing period of 12 h, 24 h, 36 h and 48 h at 1273 K in annealing temperature. The scattering mechanisms were changed with increasing the annealing periods to shift from the mixed mode of ionized impurity scattering with phonon scattering to single mode of phonon scattering for the temperature range from 300 K to 650 K. For the samples of more than 36 h in annealing period the phonon scattering mode was dominant for overall temperature range similar to that for a single crystal sample of undoped chromium disilicide. It was clarified that the annealing period highly affected thermoelectric performance and temperature dependence of thermoelectric properties and the optimum annealing process surely existed for 0.9 atm% Ag-doped, hot-press sintered CrSi/sub 2/ system. For example, the power factor was obtained 2.5/spl times/10/sup -3/ W/m/sup 2/K at 800 K in maximum for the sample of 24 h in annealing period, while it was 1.5/spl times/10/sup -3/ W/m/sup 2/K at 650 K in maximum for the hot-press sintered sample of no heat treatment.