“The intrinsic thermal conductivity of SnSe”
Academia Sinica Press 2016/11/7
In 2014 Zhao et al. 1 at Northwestern University reported that they have found an ultralow thermal conductivity (<0.4Wm-1K-1 at 923 K) and high thermoelectric figure of merit (ZT~2.6±0.3 at 923 K) in SnSe crystals, and have the results published in Nature (17 April VOL 508, Nature 375). Indeed, it is a breaking news to the world because the ZT2.6±0.3 (represents thermoelectric performance) is a world record for the thermoelectric materials (ZT=2.4 for super lattice Bi2Te3-Sb2Te3) ever found, especially for the pure bulk crystal (maximum ZT=1). The ZT2.6 stands for that the material is an excellent green energy thermoelectric material and has the capability of transfer heat to electricity with efficiency >20% which almost compete with the best solar cell nowadays. Unfortunately, no any group can reproduce the record high figure of merit ZT of SnSe.
The material is shortly studied by the Dr. Chen group in the institute of physics, Academia Sinica, they found the maximum ZT~1, then Dr. Rao group in Clemson joins the study. After carefully compare the data of our and those of Zhao et al, we deduce that their samples are not fully dense (5.4 g/cm3 which is only 87% of the theoretical value 6.2 g/cm3) and thus not truly single crystalline, implying that their reported thermal conductivities are not intrinsic to SnSe. After found the discrepancy of their SnSe crystal is not true single crystal of SnSe, we raised the issue and prepared a complete evidence and analysis to the Nature, and have our discovery released in the Nature (3 NOVEMBER 2016 VOL 539 NATURE E1).
In this work, we have grown the best SnSe single crystal in the world, and reported the intrinsic thermal conductivity of SnSe. This research work offers a better understanding of the SnSe crystal, and warrants further investigation into intrinsic thermal transport in SnSe single crystals and its use as a thermoelectric material.
Journal Links: http://www.nature.com/nature/journal/v539/n7627/full/nature19832.html
WebSite: http://www.nature.com/nature/journal/v539/n7627/full/nature19832.html
WebSite: http://www.nature.com/nature/journal/v539/n7627/full/nature19832.html