Superstrengthening Bi_2Te_3 through Nanotwinning
Guodong Li, Umut Aydemir, Sergey I. Morozov, Max Wood, Qi An, Pengcheng Zhai, Qingjie Zhang, William A. Goddard III, G. Jeffrey Snyder
Abstract
Bismuth telluride (Bi_2Te_3) based thermoelectric (TE) materials have been commercialized successfully as solid-state power generators, but their low mechanical strength suggests that these materials may not be reliable for long-term use in TE devices. Here we use density functional theory to show that the ideal shear strength of Bi_2Te_3 can be significantly enhanced up to 215% by imposing nanoscale twins. We reveal that the origin of the low strength in single crystalline Bi_2Te_3 is the weak van der Waals interaction between the Te1 coupling two Te1─Bi─Te2─Bi─Te1 five-layer quint substructures. However, we demonstrate here a surprising result that forming twin boundaries between the Te1 atoms of adjacent quints greatly strengthens the interaction between them, leading to a tripling of the ideal shear strength in nanotwinned Bi_2Te_3 (0.6 GPa) compared to that in the single crystalline material (0.19 GPa). This grain boundary engineering strategy opens a new pathway for designing robust Bi_2Te_3 TE semiconductors for high-performance TE devices.
Group Members
Li, G., Aydemir, U., Morozov, S. I., Wood, M., An, Q., Zhai, P., Zhang, Q., III, W. A. G., & Snyder, G. J. (2017). Superstrengthening Bi_2Te_3 through Nanotwinning. *Phys. Rev. Lett.*, *119*(8), Art. No. 085501.