Investigation on the thermoelectric properties of nanostructured Cr1−xTixSi2Cr1−xTixSi2

CrSi2 material is outstanding because of its thermoelectric properties and also because of its many optimization routes. Indeed, its thermal conductivity at room temperature is about 9 W m−1 K−1 with a ZT of 0.25. In this paper we propose to decrease the thermal conductivity by nanostructuration and compensate the electron scattering by increasing the charge carrier concentration with Ti. The process which permitted to get nanocrystallite of about 14 nm is presented. After cold pressing and sintering the average crystallite size reaches 50 nm with a porosity of 70%. Nanostructuring and porosity to a lesser extent lead to a strong decrease of the thermal conductivity up to 0.9±0.15 W m−1 K−1 for pure CrSi2. A significant enhancement of the power factor from 1.25μWcm−1K−2 for pure nano-CrSi2 to 2.5μWcm−1K−2 for nano-Cr0.90Ti0.10Si2 was obtained. The stability of the different phases is also evaluated by comparing experiments with ab initio calculations.

Power factor for CrSi2 and Cr(1−x)TixSi2Cr(1−x)TixSi2 for x=0.03, 0.06, 0.1, 0.15. We see that the optimum is obtained for 10% Ti doping. If we compare it with the power factor of CrSi2 it is increased by a factor 2 at 800 K.Figure optionsDownload as PowerPoint slideHighlights
► Nano-CrSi2 Ti-doped pellets have been obtained without any residual phases.
► Thermal conductivity is decreased by a factor 10 when the grain size is about 50 nm.
► Experimental results and simulation of the structure stability are in good agreement.
► The electrical resistivity is strongly reduced by a factor 3 at 600 K by Ti-doping.
► We report an enhancement of the power factor by a factor 2 for 10% Ti-doping.