Electronic Structure and Thermoelectric Power Factor of Na$_{x}$CoO$_{2}$ from First-Principles Calculation
Peng-Xian Lu1**, Rui-Xia Zhao2
1College of Materials Science and Engineering, Henan University of Technology, Zhengzhou 450001 2Department of Civil Engineering and Architecture, Henan Technical College of Construction, Zhengzhou 450001
Abstract：To investigate the relationship between the electronic structure and the power factor of Na$_{x}$CoO$_{2}$ ($x=0.3$, 0.5 and 1.0), the first-principles calculation is conducted by using density functional theory and the semi-classical Boltzmann theory. Our results suggest that with the decreasing Na content, a transition from semiconductor to semimetal is observed. Na$_{0.3}$CoO$_{2}$ possesses a higher electrical conductivity at 1000 K due to its increased density of states near the Fermi energy level. However, an optimal Seebeck coefficient at 1000 K is obtained in Na$_{0.5}$CoO$_{2}$ because of its broadened band gap near the Fermi energy level. Consequently, a maximum power factor is realized in Na$_{0.5}$CoO$_{2}$. Thus our work provides a complete understanding of the relationship between the electronic structure and the thermoelectric power factor of Na$_{x}$CoO$_{2}$.
Yakabe H, Fujita K, Nakamura K and Kikuchi K 1998 Int. Conf. Thermoelectrics (IEEE Service Center, Piscataway NJ United States, 24–28 May 1998) p 551
[10]
Mrotzek A, Muller E, Plewa J and Altenburg H 2003 International Conference On-ict (IEEE Service Center, La Grande Motte France, 17–21 August 2003) p 219
Stiewe C, Bertini L, Toprak M, Christensen M, Platzek D, Williams S, Gatti C, Müller E, Iversen B B, Muhammed M and Rowe M 2005 J. Appl. Phys.97 044317
2017, Vol. 34 
