Structure and high-temperature thermoelectric properties of the n-type layered oxide Ca 2-x Bi x-δ MnO 4-γ

F. Kawashima, X. Y. Huang, K. Hayashi, Y. Miyazaki, T. Kajitani

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

We have investigated the effects of Bi doping on the crystal structure and high-temperature thermoelectric properties of the n-type layered oxide Ca 2MnO 4-γ. The electrical conductivity σ and the absolute value of the Seebeck coefficient S were, respectively, found to increase and decrease with Bi doping. The thermal conductivity κ of doped Ca 2MnO 4-γ is relatively low, 0.5 W/m K to 1.8 W/m K (27°C to 827°C). Consequently, the ZT value, ZT = σS 2 T/κ, increases with Bi doping. The maximum ZT is 0.023 for Ca 1.6Bi 0.18MnO 4-γ at 877°C, which is ten times higher than that of the end member, Ca 2MnO 4-γ. The increase of ZT mainly results from the considerable increase of σ, which can be explained in terms of structural change. The?Mn-O(1) and the Mn-O(2) distances in the c-direction and ab-plane, respectively, increase with increasing Bi concentration, indicating that the valence state of Mn ions decreases with the increase of electron carriers in the CaMnO 3 layers. In addition, the Mn-O(2)-Mn bond angle increases linearly with Bi doping, leading to an improvement of the electron carrier mobility.

Original languageEnglish
Pages (from-to)1159-1162
Number of pages4
JournalJournal of Electronic Materials
Volume38
Issue number7
DOIs
Publication statusPublished - 2009 Jul

Keywords

  • Ca Bi MnO
  • Crystal structure
  • N-Type layered oxide
  • Thermoelectric properties

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering
  • Materials Chemistry

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