Microstructure and Thermoelectric Properties of Mechanically Robust PbTe-Si Eutectic Composites

Abstract

The microstructure and thermoelectric properties of the PbTe-Si eutectic system are presented in detail. When rapidly quenched from the melt this system yields materials with thermoelectric properties similar to PbTe itself but with improved mechanical properties. Doping optimization was performed using PbI2 as an n-type dopant giving precise control of the thermoelectric properties. Electron microscopy indicates that the PbTe-Si system is both a nanocomposite and microcomposite. Despite the added Si, the thermal conductivity of this composite follows closely that of PbTe. The temperature dependence of the Lorenz number was estimated, and it shows a significant departure from the value of metals (L 0) reaching only 45% of L 0 at 650 K. The optimized ZT for the PbTe-Si(8%) eutectic was 0.9 at 675 K. The improved mechanical robustness of these composites makes them attractive for use in large scale thermoelectric device fabrication.

Electron Microscopy for Characterization of Thermoelectric Nanomaterials

“…These eutectic mixtures after quenched exhibit considerably stronger mechanical strength and reduced brittleness compared to PbTe itself while at the same time they possess lower k lat . ZT values approaching 1.3 at 778 K for PbTe (5 %) Ge 0.8 Si 0.2 and 0.9 at 675 K for PbTe (8 %) Si can be obtained [34,35].…”

“…The biggest advances in this field have been achieved in nanostructured PbTe-based materials in which very low k can be obtained, resulting in the highest ZT values among all TEs. To date, both n-type (e.g., AgPb m SbTe m+2 (LAST) [28,30], Pb 1-x Sn x Te-PbS [31], PbTe-CdTe [32], PbTe-PbS [33], PbTe-Ge/GeSi/Si [34,35], and PbTe-Ag 2 Te [36]) and p-type (e.g., AgPb m Sn n SbTe m+n+2 (LASTT) [29,37], PbTe 1-x Se x [38], NaPb m SbTe m+2 (SALT) [39], PbTe-XTe (X ¼ Mg [40], Ca [41], Sr [42,43], Ba [41,44]), PbTe-PbS [45][46][47], and PbTe-PbSnS 2 [48,49]) materials have been developed. These materials above, the leading commercialized TE materials as well as those poised for commercialization in the near future, however, all contain a significant amount of Te or Ge, which is scarce in the earth's crust.…”

“…Detailed sample preparation of doped PbTe [83,84], PbTe + XTe (X ¼ Mg, Ca, Sr, Ba, Cd) [32,[40][41][42][43][44], PbTe + PbS [33,[45][46][47], PbTe + PbSnS 2 [48,49], PbTe + X (X ¼ Pb, Sb, Bi, Si/Ge) [34,35,85,86], TAGS [87], LAST(T) [88], SALT [89,90], and PbTe-Sb 2 Te 3 [91] can be found in corresponding literatures, which will be discussed in the following sections.…”

“…As a consequence of the degeneracy due to the rhombohedral distortion, the {110} mirror planes within the cubic system are now potential twin planes [9]. [34] The room temperature and 600 KXRD patterns for as-solidified TAGS-85 are shown in Fig. 10.36a, b, which were indexed as the low-temperature rhombohedral and high-temperature cubic polymorph, respectively.…”

Improving the thermoelectric performance of TiNiSn half-Heusler via incorporating submicron lamellae eutectic phase of Ti70.5Fe29.5: a new strategy for enhancing the power factor and reducing the thermal conductivity

“…[37][38][39][40][41][42][43] The use of such a microstructure to reduce thermal conductivity in thermoelectric materials has also been investigated. [42][43][44] The partitioning of quenched metastable phases into eutectic composite phases during a controlled process has also been well studied by Wu et al, 45 to reveal ne microstructure for enhancing the thermoelectric performance.…”