On the excess oxygen in four-layered rock-salt-type units of modulated thermoelectric Bi-Sr-(Co,Rh)-O compounds

Kunio Yubuta, Yuzuru Miyazaki, Ichiro Terasaki, Tsuyoshi Kajitani

Research output: Contribution to journalArticlepeer-review

Abstract

Excess oxygen exists in four-layered rock-salt (RS)-type units of modulated misfit-layered Bi-Sr-(Co,Rh)-O compounds, which consist of interpenetrating CdI 2-type (Co,Rh)O 2 and distorted four-layered RS-type block subsystems, which have two b-axes, i.e., b 1 and b 2, respectively. From carefully determined chemical contents and misfit ratios, p = b 1/b 2, two structural characteristics are concluded, namely, intermixing metal ions in the RS-type layers and excess oxygen δ in, or in the vicinity of, them. The chemical formulae are proposed as [(Bi 1-x (Co,Rh) x ) 2(Sr 1-y Bi y ) 2O 4+δ ] p (Co,Rh)O 2. The valence states of?cobalt and rhodium ions are close to 3.3+. These valence states are quite reasonable for good thermoelectric oxides, such as γ-Na 0.7CoO 2 and [Ca 2CoO 3] 0.62CoO 2. Excess oxygen would cause the undulated atomic arrangement.

Original languageEnglish
Pages (from-to)1116-1120
Number of pages5
JournalJournal of Electronic Materials
Volume38
Issue number7
DOIs
Publication statusPublished - 2009 Jul 1

Keywords

  • Chemical composition
  • Electron diffraction
  • High-resolution electron microscopy image
  • Misfit-layered structure
  • Valence state

ASJC Scopus subject areas

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

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