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Synthesis and Thermoelectric Properties of NaxCo2O4 Single Crystals

Published online by Cambridge University Press:  01 February 2011

Jian He ,
Kelvin Aaron ,
Edward Abbott ,
Joseph Kolis  and
Terry M. Tritt
Jian He
Affiliation:
ttritt@clemson.edu, Clemson University, Physics and Astronomy, 118 Kinard Physics Lab, Clemson, SC, 29634, United States, 1-864-6564597, 1-864-6560805
Kelvin Aaron
Affiliation:
kaaron@CLEMSON.EDU, Clemson University, Physics and Astronomy, United States
Edward Abbott
Affiliation:
caped@juno.com, Clemson University, Chemistry, United States
Joseph Kolis
Affiliation:
kjoseph@CLEMSON.EDU, Clemson University, Chemistry, United States
Terry M. Tritt
Affiliation:
ttritt@clemson.edu, Clemson University, Physics and Astronomy, United States
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Abstract

Single crystal NaCo2O4 platelets with sizes up to 6mm were synthesized by the typical high temperature NaCl flux method. The in-plane thermopower α and in-plane resistivity ρ were measured to be ∼100µV/K and 0.3mΩ-cm at 300K, respectively. The in-plane thermal conductivity κ was measured by our custom-designed “PTC” system and found to be ∼5 W-m−1K−1 at 300K, which is 2-3 times larger than the polycrystalline NaCo2O4. The in-plane phonon mean free path lph was estimated to be ∼9.5Å, which is much smaller than the in-plane mean free path of conducting carriers (la∼51Å). A novel low temperature flux method where NaCl/NaOH was used as flux and metallic Co powders as Co source was developed to successfully synthesize Na-deficient NaxCo2O4 crystals with size up to 6mm at low temperature of 550°C. The different temperature dependence in resistivity reveals that two different types of crystals can exist, one is metallic and another is semiconducting. The temperature dependence of the measured k is like that of a disordered solid and the value is found to be ∼7 W-m−1K−1 at 300K.

Keywords

thermoelectricityoxidethermal conductivity
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 886: Symposium F – Materials and Technologies fore Direct Thermal-to-Electric Energy Conversion , 2005 , 0886-F02-04
Copyright
Copyright © Materials Research Society 2006

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References

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