Evaporation-condensation effects on the thermoelectric performance of PbTe-based couples

In thermoelectric (TE) generators, Carnot efficiency maximization, by increasing the hot side temperature, is required for maximizing the heat to electricity energy conversion. Yet, volatile species sublimation, apparent in many TE material classes including tellurides, selenides, sulfides, silicides and more, limits the hot side temperature to a certain level, depending on the specific composition. In the current research, the TE performance of a PbTe-based couple subjected to a large temperature difference of an extreme hot side temperature of 600 degrees C and cold side temperature of 60 degrees C for 456 h was investigated both experimentally and theoretically and was correlated to evaporation-condensation effects in the vicinity of the hot-side temperature. Only moderate degradation of the maximal electrical power and efficiency was observed showing the promising potential of employing of such couples in practical TE applications.