Résumé
Conventional thermoelectric materials such as Bi 2 Te 3 have the best performances at room temperature and can reach a ZT about 1 [1]. However, the cost, the toxicity and the scarcity of Te limit the application of thermoelectric materials in the low temperature range (300 -600K). The use of ecofriendly elements such as silicides alloys could overcome these concerns. Among them Mn-Si and Mg 2 (Si,Sn) reached a maximum figure of merit of 0.63 (723 K) and 0.8 (650 K) respectively [2,3] and α-SrSi 2 reaches a ZT about 0.15 at 300K which is the highest value for a silicide alloy at this temperature. The power factor of α-SrSi 2 is close to that of Bi 2 Te 3 however its thermal conductivity (~5 W/m.K) limit its performances.
In this work, we investigate the effect of the nanostructuring, Sr purity and substitution on the thermal and thermoelectric properties of α-SrSi 2 combining different metallurgical technics. We have shown that the nanostructuring enables to decrease strongly the lattice thermal conductivity of this compound close to that expected to highly disordered or amorphous materials without impacting much the power factor. This work leads to an increase of the figure of merit to about 60% compared to our bulk reference.