We report the electrical and thermal properties of β-pyrochlore (defect pyrochlore) oxides AFe0.33W1.67O6 (A = K, Rb, Cs) with a crystal structure having a small cation surrounded by oversized cage-like framework. The thermal conductivity, κ, of CsFe0.33W1.67O6 and RbFe0.33W1.67O6 showed extremely low values as oxides (below 1.0 W/mK) similar to those of ATaWO6 (A = K, Rb, Cs) which we have already reported. These low κ values are ascribed to a “rattling” motion of the A cations, evidenced by their crystal structure refinement and the Raman spectra. Their electrical conductivity, σ, was in the order of 10−3 S/cm, and the Seebeck coefficient, S, was −500 to −600 μV/K. The electrical conductivity of AFe0.33W1.67O6 (A = Rb, Cs) was much higher than those of ATaWO6 (A = Rb, Cs), suggesting that an appropriate selection of the framework composition enables us to have better thermoelectric performance.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Materials Chemistry