Recently, Yingdong Guan, the undergraduate student of the Physics Department, published the latest research result on the discovery of high-performance AgBiSe2 based thermoelectric materials as the first author on Applied Physics Letters (Nature Index). Title of the paper is " Enhanced Thermoelectric Performance Realized in AgBiS2 Composited AgBiSe2 through Indium doping and Mechanical Alloying". 

The Thermoelectric effects provides direct transition between thermal energy and electrical energy, thus has grasped great attentions at the background of energy crisis and environmental issue as a clean and effective route of energy transfer. Compare to traditional thermoelectric material, I−V−VI2 (I=Ag; V=Sb, Bi; and VI=S, Se, Te) semiconductor own intrinsically low lattice thermal conductivity; thus, Pb-free I−V−VI2 has attracted much attention as a potential thermoelectric material system. Though AgSbTe2 is the most widely studied one among I−V−VI2 composites, however, AgSbTe2 may be limited in application because it contains a considerable amount of Tellurium, which is a kind of scarce metal; thus, a relative inexpensive and more stable compound AgBiSe2 has been investigated intensively nowadays. In previous report, attempts to enhance electrical proprieties of AgBiSe2 system are all focused on element doping. Here we made another attempt by reducing the lattice thermal conductivity of AgBiSe2 system through AgBiS2 compositing and mechanical ball milling. Through this method, we achieved significant reduction of thermal conductivity from ~0.5 W/mK to 0.33 W/mK at 773 K, which is the record low value ever reported in this specific system. Combining with in dope to control electric properties, we eventually achieved a ZT as high as 0.95 at 773 K, which is comparable with the reported highest ZT value of AgBiSe2 system. This method of realizing polyphase solid solution through ball milling has also provided an alterative thought for other researchers to enhance thermoelectric performance in their research.

Electric and thermal properties of hand-milled and ball-milled samples

Guan Yingdong is an undergraduate in Physics Department of our university. He will graduate in July this year and further his study in Penn State University. Since he joined professor Jiaqing He’s group in the Department of physics in the second semester of the sophomore year, under the guidance of Professor He Jiaqing and Research Assistant professor Wu Di (now a professor in Shanxi Normal University), he completed most of the experimental research as well as paper writing independently. 

This work was supported by the Natural Science Foundation of Guangdong Province, and the Science, Technology and Innovation Commission of Shenzhen Municipality, the National Natural Science Foundation of China, and also partly by the Fundamental Research Funds for the Central Universities.