TY - JOUR
T1 - Higher thermoelectric performance of Zintl phases (Eu0.5Yb0.5)1-xCaxMg2Bi2 by band engineering and strain fluctuation
AU - Shuai, Jing
AU - Geng, Huiyuan
AU - Lan, Yucheng
AU - Zhu, Zhuan
AU - Wang, Chao
AU - Liu, Zihang
AU - Bao, Jiming
AU - Chu, Ching Wu
AU - Sui, Jiehe
AU - Ren, Zhifeng
N1 - Funding Information:
The work performed at University of Houston is funded by the US Department of Energy under Contract DE-FG02-13ER46917/DE-SC0010831 and supported in part by US Air Force Office of Scientific Research Grant FA9550-15-1-0236, National Science Foundation (Career Award ECCS-1240510), the Robert A. Welch Foundation (E-1728), the T.L.L. Temple Foundation, the John J. and Rebecca Moores Endowment, and the State of Texas through the Texas Center for Superconductivity at the University of Houston. This work was also supported by the National Natural Science Foundation of China (51471061).
PY - 2016/7/19
Y1 - 2016/7/19
N2 - Complex Zintl phases, especially antimony (Sb)-based YbZn0.4Cd1 6Sb2 with figure-of-merit (ZT) of ∼1.2 at 700 K, are good candidates as thermoelectric materials because of their intrinsic "electron-crystal, phonon-glass" nature. Here, we report the rarely studied p-type bismuth (Bi)-based Zintl phases (Ca,Yb,Eu)Mg2Bi2 with a record thermoelectric performance. Phase-pure EuMg2Bi2 is successfully prepared with suppressed bipolar effect to reach ZT ∼ 1. Further partial substitution of Eu by Ca and Yb enhanced ZT to ∼1.3 for Eu0.2Yb0.2Ca0.6Mg2Bi2 at 873 K. Density-functional theory (DFT) simulation indicates the alloying has no effect on the valence band, but does affect the conduction band. Such band engineering results in good p-type thermoelectric properties with high carrier mobility. Using transmission electron microscopy, various types of strains are observed and are believed to be due to atomic mass and size fluctuations. Point defects, strain, dislocations, and nanostructures jointly contribute to phonon scattering, confirmed by the semiclassical theoretical calculations based on a modified Debye-Callaway model of lattice thermal conductivity. This work indicates Bi-based (Ca, Yb,Eu)Mg2Bi2 is better than the Sb-based Zintl phases.
AB - Complex Zintl phases, especially antimony (Sb)-based YbZn0.4Cd1 6Sb2 with figure-of-merit (ZT) of ∼1.2 at 700 K, are good candidates as thermoelectric materials because of their intrinsic "electron-crystal, phonon-glass" nature. Here, we report the rarely studied p-type bismuth (Bi)-based Zintl phases (Ca,Yb,Eu)Mg2Bi2 with a record thermoelectric performance. Phase-pure EuMg2Bi2 is successfully prepared with suppressed bipolar effect to reach ZT ∼ 1. Further partial substitution of Eu by Ca and Yb enhanced ZT to ∼1.3 for Eu0.2Yb0.2Ca0.6Mg2Bi2 at 873 K. Density-functional theory (DFT) simulation indicates the alloying has no effect on the valence band, but does affect the conduction band. Such band engineering results in good p-type thermoelectric properties with high carrier mobility. Using transmission electron microscopy, various types of strains are observed and are believed to be due to atomic mass and size fluctuations. Point defects, strain, dislocations, and nanostructures jointly contribute to phonon scattering, confirmed by the semiclassical theoretical calculations based on a modified Debye-Callaway model of lattice thermal conductivity. This work indicates Bi-based (Ca, Yb,Eu)Mg2Bi2 is better than the Sb-based Zintl phases.
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U2 - 10.1073/pnas.1608794113
DO - 10.1073/pnas.1608794113
M3 - Article
AN - SCOPUS:84978807252
SN - 0027-8424
VL - 113
SP - E4125-E4132
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 29
ER -