We observe two distinct phases of Nax CoO2 in the large Na-doping region (x ≥ 0.75), a pure phase H2, and a mixed phase H2 + H3. The H2 phase is characterized by a steep increase of the Peltier conductivity α defined as J = α (- ∇ T), where J the thermoelectric current driven by the temperature gradient - ∇ T. The mixed-phase state H2 + H3 exhibits an unusual layered phase separation with conducting layers existing in parallel with insulating ones. At the critical doping xp ∼ 0.85, the figure-of-merit Z at 80 K is 40 times larger than that of the as-grown sample (x ∼ 0.7). The Hall coefficient and magnetoresistance are also reported.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Hall effect
- Mixed phase