High Thermopower with Metallic Conductivity in p-Type Li-Substituted PbPdO2

Published

May 9, 2016

Author(s)

Leo K. Lamontagne, Geneva Laurita, Michael W. Gaultois, Michael Knight, Leila Ghadbeigi, Taylor D. Sparks, Markus E. Gruner, Rossitza Pentcheva, Craig Brown, Ram Seshadri

Abstract

PbPdO₂ is a band semiconductor with a band gap arising from the filled d⁸ nature of square-planar Pd²⁺. We establish that hole doping through Li substitution for Pd in PbPdO₂ results in a p-type metallic oxide with a positive temperature coefficient of resistance for substitution amounts as small as 2 mol % of Li for Pd. Furthermore, PbPd_1-xLi_xO₂ demonstrates a high Seebeck coefficient, and is therefore an oxide thermoelectric material with high thermopower despite the metallic conductivity. Up to 4 mol % Li is found to substitute for Pd as verified by Rietveld refinement of neutron diffraction data. At this maximum Li-substitution, the resistivity is driven below the Mott metallic maximum to 3.5x10^-3Ω} cm with a Seebeck coefficient of 115υV/K at room temperature which increases to 175 υV/K at 600 K. These electrical properties are almost identical to the well-known p-type oxide thermoelectric Na_xCoO₂. In contrast to the cobalt oxides, non-magnetic LI-substituted PbPdO₂ does not possess the spin entropy responsible for the high performance in the cobaltate compounds. This suggests that there are other avenues to achieving high Seebeck coefficients in oxide thermoelectrics. The electrical properties coupled with the moderately low lattice thermal conductivities allow for a zT = 0.12 at 600 K, the maximum temperature measured here. The trend suggests yet higher values at elevated temperatures.

Citation

Chemistry of Materials

Volume

28

Issue

10

Pub Type

Journals

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Keywords

thermoelectric, neutron diffraction, substitution, structre

Citation

Lamontagne, L. , Laurita, G. , Gaultois, M. , Knight, M. , Ghadbeigi, L. , Sparks, T. , Gruner, M. , Pentcheva, R. , Brown, C. and Seshadri, R. (2016), High Thermopower with Metallic Conductivity in p-Type Li-Substituted PbPdO₂, Chemistry of Materials, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=919970 (Accessed April 26, 2024)