title: Valence Band Modification and High Thermoelectric Performance in SnTe Heavily Alloyed with MnTe.
abstract: We demonstrate a high solubility limit of >9 mol% for MnTe alloying in SnTe. The electrical conductivity of SnTe decreases gradually while the Seebeck coefficient increases remarkably with increasing MnTe content, leading to enhanced power factors. The room-temperature Seebeck coefficients of Mn-doped SnTe are significantly higher than those predicted by theoretical Pisarenko plots for pure SnTe, indicating a modified band structure. The high-temperature Hall data of Sn1-xMnxTe show strong temperature dependence, suggestive of a two-valence-band conduction behavior. Moreover, the peak temperature of the Hall plot of Sn1-xMnxTe shifts toward lower temperature as MnTe content is increased, which is clear evidence of decreased energy separation (band convergence) between the two valence bands. The first-principles electronic structure calculations based on density functional theory also support this point. The higher doping fraction (>9%) of Mn in comparison with ∼3% for Cd and Hg in SnTe gives rise to a much better valence band convergence that is responsible for the observed highest Seebeck coefficient of ∼230 μV/K at 900 K. The high doping fraction of Mn in SnTe also creates stronger point defect scattering, which when combined with ubiquitous endotaxial MnTe nanostructures when the solubility of Mn is exceeded scatters a wide spectrum of phonons for a low lattice thermal conductivity of 0.9 W m(-1) K(-1) at 800 K. The synergistic role that Mn plays in regulating the electron and phonon transport of SnTe yields a high thermoelectric figure of merit of 1.3 at 900 K.
authors: Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
authors: Gangjian
authors: G
authors: Tan
authors: Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States.
authors: Fengyuan
authors: F
authors: Shi
authors: Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States.
authors: Shiqiang
authors: S
authors: Hao
authors: Department of Physics, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors: Hang
authors: H
authors: Chi
authors: Department of Physics, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors: Trevor P
authors: TP
authors: Bailey
authors: School of Materials Science and Engineering, Beihang University , Beijing 100191, China.
authors: Li-Dong
authors: LD
authors: Zhao
authors: Department of Physics, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors: Ctirad
authors: C
authors: Uher
authors: Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States.
authors: Chris
authors: C
authors: Wolverton
authors: Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States.
authors: Vinayak P
authors: VP
authors: Dravid
authors: Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.|Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors: Mercouri G
authors: MG
authors: Kanatzidis