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.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Materials Chemistry