Non-surfactant synthesis and thermoelectric performance of p-type AgxSn1-xSe nanoplates
Chia-Hua Chien1,2,3*, Chung-Chieh Chang2, Cheng-Lung Chen2, Yu-Ruei Wu2, Chun-Hao Huang2, Wei-Han Tsai2, Chih-Hao Lee1, Yang-Yuan Chen2, Maw-Kuen Wu2
1Department of Engineering and System Science, National Tsing Hua University, Hsinchu, Taiwan
2Institute of Physics, Academia Sinica, Taipei, Taiwan
3Nano Science and Technology Program, Taiwan International Graduate Program, Institute of Physics, Academia Sinica, Taipei, Taiwan
* presenting author:錢佳華,
In the high temperature range thermoelectric applications, the lead chalcogenide thermoelectric semiconductors have been demonstrated around 500 K such as PbS, PbSe and PbTe. Although the highest zTs are seen in these materials, the toxicity of lead is still a challenge in domestic applications. Recently however, lead-free compounds SnSe have been discovered to be the good thermoelectric materials because of the intrinsic low thermal conductivity [1]. Here, we report that the p-type SnSe nanoplates doped with Ag prepared by a two-step surfactant-free chemical method and consolidated by spark plasma sintering (SPS) technique. From X-ray diffration data of all samples and selection area electron diffraction (SAED) combined with high-resolutin TEM, it can be pointed out the single crystal SnSe crystallizes in 2D structure with the orthorombic Pnma. Comparing with the SnSe polycrystals which are prepared by melting and hot pressing[2], the transport properties are different. The electrical resistivity of SnSe nanocomposite(~300 μΩ-m) is two times smaller than the bulk (~600 μΩ-m) at 650 K, especilly, Seebeck coefficient is linear temperature dependant increase from 186 μV/K at 300 K to 300 μV/K at 650 K. Due to the nanoscale grains in the nanocomposites, the thermal conductivity is as low as 0.52 W/mK at 650 K. Also, The zT value is around 0.38 at this temperature. In addition, Ag can compensate for the inherent Sn vacancies in the lattice and increase the electrical conductivity. In the report the effect of dopant amount on the transport properties will be discussed.

Keywords: SnSe, Thermoelectric, Seebeck coefficient, nanocomposite