Property-processing relations in developing thermoelectric ceramics: Na1-x Co2O4

Hiroo Yamakawa, Soonil Lee, Hiroshi Takagi, Clive A. Randall

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Abstract

Polycrystalline Na1-x Co2O4 is a promising p-type oxide thermoelectric, and it was investigated in a property-processing study to enhance the thermoelectric properties for high temperature applications. The density of the ceramics was improved by a post-milling process, and consequently, we obtained better thermoelectric power factors (PF) due to an associated improvement in electrical conductivity. Through a milling process, and sintering at 1203 K, we obtained an enhanced thermoelectric power factor of ~4 μW/cm K2 at 500 K for randomly orientated polycrystalline ceramics. The Seebeck coefficient variation with temperature demonstrates through modeling that the conduction mechanism changed from metallic to a semiconducting behavior between temperatures 300 to 400 K.

Original languageEnglish (US)
Pages (from-to)2064-2070
Number of pages7
JournalJournal of Materials Science
Volume46
Issue number7
DOIs
StatePublished - Apr 1 2011

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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