Defect-Controlled Electronic Structure and Phase Stability in Thermoelectric Skutterudite CoSb_3
Guodong Li, Umut Aydemir, Max Wood, William A. Goddard III, Pengcheng Zhai, Qingjie Zhang, G. Jeffrey Snyder
Abstract
Controlling extrinsic defects to tune the carrier concentration of electrons or holes is a crucial point concerning the engineering application of thermoelectric semiconductors. To understand the defect-controlled electronic structure in thermoelectric materials, we apply density functional theory (DFT) to investigate the defect chemistry of dopants M (M = O, S, Se, Te) in CoSb_3. DFT predicts that the breakage of Sb_4-rings induced by these dopants produces the unexpected (n- or p-type) conductivity behavior in CoSb_3. For example, energetically dominant O interstitials (Oi) chemically break Sb_4-rings and form O-4Sb five-membered rings, leading to the charge neutral behavior of O_i. While S interstitials (S_i) collapse Te-3Sb four-membered rings within Te doped CoSb_3 leading to a p-type conduction behavior, Se substitution on Sb (Se_(Sb)) breaks the Se-Te-2Sb four-membered ring resulting in a charge neutral behavior of the complex defect Se_(Sb)+Te_(Sb). Furthermore, the solubility limits of M dopants (M = S, Se, Te) are also calculated to provide essential information on single-phase material design. This study provides a new insight to understand the complicated chemical structure in doped CoSb_3, which is beneficial for devising effective doping strategies to develop high-performance bulk thermoelectric materials.
Group Members
Li, G., Aydemir, U., Wood, M., III, W. A. G., Zhai, P., Zhang, Q., & Snyder, G. J. (2017). Defect-Controlled Electronic Structure and Phase Stability in Thermoelectric Skutterudite CoSb_3. *Chemistry of Materials*, *29*(9), 3999-4007.