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Published February 21, 2016 | Supplemental Material + Published
Journal Article Open

YCuTe_2: a member of a new class of thermoelectric materials with CuTe_4-based layered structure

Abstract

Intrinsically doped samples of YCuTe_2 were prepared by solid state reaction of the elements. Based on the differential scanning calorimetry and the high temperature X-ray diffraction analyses, YCuTe_2 exhibits a first order phase transition at ∼440 K from a low-temperature-phase crystallizing in the space group P^(bar)3 with combining P^(bar)3m1 to a high-temperature-phase in P^(bar)3 with combining macron]. Above the phase transition temperature, partially ordered Cu atoms become completely disordered in the crystal structure. Small increases to the Cu content are observed to favour the formation of the high temperature phase. We find no indication of superionic Cu ions as for binary copper chalcogenides (e.g., Cu_2Se or Cu_2Te). All investigated samples exhibit very low thermal conductivities (as low as ∼0.5 W m^(−1) K^(−1) at 800 K) due to highly disordered Cu atoms. Electronic structure calculations are employed to better understand the high thermoelectric efficiency for YCuTe_2. The maximum thermoelectric figure of merit, zT, is measured to be ∼0.75 at 780 K for Y_(0.96)Cu_(1.08)Te_2, which is promising for mid-temperature thermoelectric applications.

Additional Information

© 2016 Royal Society of Chemistry. Received 16th December 2015. Accepted 22nd January 2016. First published on the web 1st February 2016. This work was intellectually led by the Materials Project which is supported by the Department of Energy Basic Energy Sciences program under Grant No. EDCBEE, DOE Contract DE-AC02-05CH11231. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy. We would like to thank Dr Timothy Davenport for his assistance in HT-XRD measurements. U. A. acknowledges the financial assistance of The Scientific and Technological Research Council of Turkey. J.-H. P. acknowledges the Dalhousie Research in Energy, Advanced Materials and Sustainability (DREAMS) NSERC CREATE program, and M. B. Johnson's assistance. M. A. W. acknowledges the support of NSERC, and Dalhousie University's Institute for Research in Materials and its Facilities for Materials Characterization. G. H. acknowledges the F. R. S.-FNRS and the European Union Marie Curie Career Integration (CIG) grant HTforTCOs PCIG11-GA-2012-321988 for financial support. A. J. was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Early Career Research Program. Optical measurements in this work were performed at the Molecular Materials Research Center (MMRC) in the Beckman Institute at the California Institute of Technology.

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