Maximizing the performance of n-type Mg3Bi2 based materials for room-temperature power generation and thermoelectric cooling

Abstract

Although the thermoelectric effect was discovered around 200 years ago, the main application in practice is thermoelectric cooling using the traditional Bi2Te3. The related studies of new and efficient room-temperature thermoelectric materials and modules have, however, not come to fruition yet. In this work, the electronic properties of n-type Mg3.2Bi1.5Sb0.5 material are maximized via delicate microstructural design with the aim of eliminating the thermal grain boundary resistance, eventually leading to a high zT above 1 over a broad temperature range from 323 K to 423 K. Importantly, we further demonstrated a great breakthrough in the non-Bi2Te3 thermoelectric module, coupled with the high-performance p-type α-MgAgSb, for room-temperature power generation and thermoelectric cooling. A high conversion efficiency of ~2.8% at the temperature difference of 95 K and a maximum temperature difference of 56.5 K are experimentally achieved. If the interfacial contact resistance is further reduced, our non-Bi2Te3 module may rival the long-standing champion commercial Bi2Te3 system. Overall, this work represents a substantial step towards the real thermoelectric application using non-Bi2Te3 materials and devices.

Mediating Point Defects Endows n‐Type Bi2Te3 with High Thermoelectric Performance and Superior Mechanical Robustness for Power Generation Application

“…[8][9][10][11] Although some new low-temperature thermoelectric materials are recently discovered, it is still challenging for them to take the dominant position of Bi 2 Te 3 based alloys in commercial applications for cooling applications and power generation. [5,[12][13][14] Besides, the majority of Bi 2 Te 3 based alloys work in a narrow temperature range, [15] typically below 423 K, due to the strong bipolar effect.…”

Reliable metal alloy contact for Mg3+δBi1.5Sb0.5 thermoelectric devices

“…side temperature as variation of the current were recorded in Figure 6B-D, respectively. Benefiting from the low contact resistance and the properly optimized n-and p-type materials, the Mg 3+δ Bi 1.5 Sb 0.5 /Bi 0.4 Sb 1.6 Te 3 unicouple achieved conversion efficiency of ~4% at a temperature difference of 100 K [Figure 6E], which is better than the cutting-edge results reported recently [Figure 6F] [9,[39][40][41] . The highest efficiency obtained was ~6% at a temperature difference of 150 K and a hot-side temperature of 448 K. With such a decent efficiency, this unicouple already outperforms an intermediate TEG with a temperature difference of over 400 K [5,42,43] .…”

“…Here the cold-side temperature was maintained around room temperature. The open circuit voltage (V oc ), output power and heat flowing through the heat sink (Q in ) of the unicouple at different hot- , Bi 2 Te 3 -based device [9] , segmented Mg 3 Sb 2 /MgAgSb [38] , Mg 3 Bi 2 /MgAgSb [40] , and Mg 3 Sb 2 /MgAgSb ).…”

Material Descriptors to Predict Thermoelectric Performance of Narrow-gap Semiconductors and Semimetals

“…We compute the parameters in the material descriptors with density functional theory (DFT) and semi-empirical models for transport. 29,40 In addition to the Zintl phases, we also calculated the material descriptors for Mg 3 Bi 2 , which is a wellknown semimetallic TE material 11,[41][42][43] used as a benchmark material in this study. We show that Mg 3 Bi 2 is indeed a high-performing TE material near room temperature, which validates the predictive power of the descriptors.…”