Design and Fabrication of Segmented GeTe/(Bi,Sb)2Te3 Thermoelectric Module with Enhanced Conversion Efficiency

GeTe and (Bi,Sb)(2)Te-3 are two representative thermoelectric (TE) materials showing maximum performance at middle and low temperature, respectively. In order to achieve higher performance over the whole temperature range, their segmented one-leg TE modules are designed and fabricated by one-step spark plasma sintering (SPS). To search for contact and connect layers, the diffusion behavior of Fe, Ni, Cu, and Ti metal layers in GeTe is studied systematically. The results show that Ti with a similar linear expansivity (10.80 x 10(-6) K-1) to GeTe, has low contact resistance (3 mu omega cm(2)) and thin diffusion layer (0.4 mu m), and thus is an effective metallization layer for GeTe. The geometric structure of the GeTe/(Bi,Sb)(2)Te-3 segmented one-leg TE module and the ratio of GeTe to (Bi,Sb)(2)Te-3 are determined by finite element simulation method. When the GeTe height ratio is 0.66, its theoretical maximum conversion efficiency (eta(max)) can reach 15.9% without considering the thermal radiation and thermal/electrical contact resistance. The fabricated GeTe/(Bi,Sb)(2)Te-3 segmented one-leg TE module showed a eta(max) up to 9.5% with a power density approximate to 7.45 mW mm(-2), which are relatively high but lower than theoretical predictions, indicating that developing segmented TE modules is an effective approach to enhance TE conversion efficiency.