Southern University of Science and Technology (SUSTech) has had another faculty member published in renowned international academic journal Advanced Functional Materials.

This time, Associate Professor Liu Weishu of the Department of Materials Science and Engineering who saw his research group published. His research group has made breakthroughs in room temperature thermoelectric materials. The group’s paper was called “Mg3+δSbxBi2-x Family: A Promising Substitute for the State-of-the-Art n-Type Thermoelectric Materials near Room Temperature,” and was selected as the inside front cover of the next issue.

Thermoelectric devices attracted increasing attention from both the academic and industrial communities because they offer a promising solution for convenient conversion between heat and electricity. The power generation applications, such as solid‐state solar thermoelectric generator and waste heat harvester from heat sources of automotive exhaust gas, fireplace, and steel industrial, gravitated intensively academic efforts on the medium-temperature thermoelectric materials.

Figure 1: Various new materials discovered since the middle of the 20^th century

The Bi₂Te_3−xSe_x family has been known as n‐type state‐of‐the‐art thermoelectric materials near room temperature (RT) for more than half a century, which dominates the active cooling and novel heat harvesting application near RT. However, the drawbacks of a brittle nature and Te-content restrict the possibility for exploring potential applications. 

On the other hand, the industrial demands in the thermal management of microelectronic integrated circuits, photonic light‐emitting diode (LED) packaging, and the self‐powered system for the Internet of Things (IoT) sensors, also continuously encouraged the works on the room‐temperature (RT) thermoelectric materials. With continuous efforts since the 1950s, There is a long list of new thermoelectric materials, as shown in Figure 1. Among them, only p-type MgAgSb showed promise as new candidate for the thermoelectric application near RT. Unfortunately, it still contained 42 wt% noble metal silver, which was definitely not beneficial to the large-scale application.

In this work, we have experimentally showed that the Mg_3+δSb_xBi_2−x family had a comparable thermoelectric performance in terms of the average ZT or engineering ZT in the temperature of 50–250 °C, but two times higher toughness and only half cost as compared with the n‐type state-of-the-art room-temperature thermoelectric materials Bi₂Te_2.7Se_0.3. 

Figure 2 The new N-type Mg3+δ SbxBi2-x room temperature thermoelectric material.

(a) room temperature hotspot device; (b-d) thermoelectric properties; (e-f) mechanical properties

it is shown that the Mg_3+δSb_xBi_2−x family ((ZT)_avg = 1.05) could be a promising substitute for the Bi₂Te_3−xSe_x family ((ZT)_avg = 0.9–1.0) in the temperature range of 50–250 °C based on the comparable thermoelectric performance through a synergistic effect from the tunable bandgap using the alloy effect and the suppressible Mg-vacancy formation using an interstitial Mn dopant. The positive temperature dependence of the band gap suggests this family is also a superior medium‐temperature thermoelectric material for the significantly suppressed bipolar effect. Furthermore, a two times higher mechanical toughness, compared with the Bi₂Te_3−xSe_x family, allows for a promising substitute for state‐of‐the‐art n‐type thermoelectric materials near RT.

It is also worth mentioning that high-performance room temperature thermoelectric materials are listed as a key national scientific research project of the 2018 National Key Research and Development Program. Thus, the new room temperature thermoelectric materials will become the new focal point for thermoelectric materials.

Since Associate Professor Liu Weishu joined SUSTech at the end of 2016, he has carried out this research work independently in the University. The first author is research assistant Shu Rui. Liu Weishu is the correspondent author and Assistant Professor of Physics Huang Li as the co correspondent author. Associate Professor of Materials Science and Engineering Gu Meng, Professor of Physics Zhang Wenqing, Associate Research Fellow of the Institute of High Energy Xu Wei, Senior Engineer of Beijing Aviation Materials Institute Liu Yong, and Associate Researcher of Synchrotron Radiation Shanghai Wang Yu all made significant contributions to the research work.

The research was supported by the start-up funds of SUSTech and the key projects of the Ministry of Science and Technology and the National Natural Science Foundation.

Regarding this research, Dr. Liu Weishu also shared some of his feelings:

“SUSTech provides a good platform for cutting-edge interdisciplinary research, which allows scientists to explore interesting fundamental science together and develop useful new materials. At the same time, I am especially thankful to SUSTech for giving young people enough time to explore new directions.”

It takes about one and a half years to move from the idea to verification by experiment, theoretical analysis, contribution and acceptance of the research work. When he first submitted the research, the peer review panels required repeated experiments to ensure that the data was reliable and correct.

As the first author had gone to Europe to study, he had to ask the students from his research groups to repeat the experiment for over a month to satisfy the peer reviewers.

He commented that the road to scientific research is both torturous and surprising. After the research group had submitted their second paper on the topic, they received a response from the editor in less than a month, accepting it in its entirety without further changes. By taking a serious attitude to their research, their efforts were approved by the editors and their scientific peers. The research group could show that they could not only repeat the experiment but could also do it better.

Article link: https://onlinelibrary.wiley.com/doi/10.1002/adfm.201807235