Enhancing thermoelectric properties of p-type SiGe by SiMo addition

Synergetic Enhancement of the Power Factor and Suppression of Lattice Thermal Conductivity via Electronic Structure Modification and Nanostructuring on a Ni- and B-Codoped p-Type Si–Ge Alloy for Thermoelectric Application

“…It implies that the sample possesses sufficient scattering centers such as nanoparticles, micrograins, defects in the lattice, and tiny precipitates to scatter the phonons of various wavelengths. It should be emphasized that the thermal conductivity in the present study is lower than those of the previously reported Si−Ge + YSi 2 , 34 Si−Ge + SiMo, 53 Si−Ge + TiB 2 , 54 and Si−Ge + CrSi 2 55 nanostructured composites, as shown in Figure 10b. The scattering process of phonons of various wavelengths is schematically shown in Figure 10c.…”

“…The Seebeck coefficient monotonically increases with increasing temperature, and therefore, the samples are naturally considered degenerate semiconductors. Sample x = 0.01 exhibits the largest value of the Seebeck coefficient of about 372 μV K −1 at 937 K. Notably, the observed value of the Seebeck coefficient is higher than the previously reported values of p-type Si−Ge + YSi 2 , 34 Si−Ge + SiMo, 53 Si−Ge + TiB 2 , 54 and Si−Ge + CrSi 2 , 55 as shown in Table 4. The Seebeck coefficient of the samples in the present study shows a small decrease in its magnitude at high temperatures above 950 K. This decrease is attributed to the electron-−hole excitation, which is often explained in terms of the "bipolar dif fusion ef fect".…”

“…The large value of ZT = 1.56 of sample x = 0.03 at 1000 K is brought about by a large PF of 2.3 mW m −1 K −2 together with low thermal conductivity of 1.47 W m −1 K −1 . The obtained maximum value of ZT for sample x = 0.03 is higher than those of Si−Ge + SiMo, 53 Si−Ge + TiB 2 , 54 and Si−Ge + CrSi 2 , 55 as shown in Figure 11c. On the other hand, the highest ZT value obtained in the present study is still smaller than that of Si−Ge + YSi 2 , 34 mostly due to the much higher electrical resistivity of 4.49 mΩ cm in the present study than 2.1 mΩ cm of the Si− Ge + YSi 2 .…”

Computationally Modelling the Use of Nanotechnology to Enhance the Performance of Thermoelectric Materials

“…Furthermore, using a ball milling process, the grain size can be significantly reduced and grain boundaries can be introduced, causing an increase in low frequency phonon scattering. The creation of atomic-scale point defects can also be used to enhance high frequency scattering [47]. Together, these two methods create hierarchical phonon scattering centres that reduce the value of k L further.…”

“…Neither SiGe-20% SiMo nor Yb 13.5 La 0.5 ZnSb 11 manage to achieve ZT values above 0.9, with maximum values of 0.88 at 1273 K and 0.77 at 1213 K, respectively. Although Li et al (2019) found SiGe-20% SiMo performs almost 50% better than all other additions of SiMo to SiGe when it comes to electrical conductivity, the downfall of SiGe-20% SiMo is its high thermal conductivity over the entire temperature range [45]. It starts at 4.9 Wm −1 K −1 at 273 K, only dropping below 4 Wm −1 K −1 for the first time at 1100 K, and finishes at 3.9 Wm −1 K −1 at 1273 K. Although Yb 13.5 La 0.5 ZnSb 11 does not perform the best here, the maximum ZT of 0.77 recorded for this material is almost six times greater than the maximum value of 0.13 recorded when testing Yb 14 ZnSb 11 .…”