We measure the high-temperature thermoelectric properties of the Na x CoO 2−δ single crystal for the first time. The Na x CoO 2−δ single crystals are prepared by a flux technique, and the resulting flaky single crystals are very thin on the c-axis. The inplane electrical resistivity (ρ), the thermoelectric power (S) and the in-plane thermal conductivity (κ) are measured in the range of 300 K to 800 K. The estimated power factor (PF = S 2 ·ρ −1 ) and the figure-of-merit (Z = S 2 ·ρ −1 κ −1 ) are about 2.4 mW m −1 K −2 and 0.12 mK −1 at 300 K, respectively. These factors increase with temperature, and reach the value of PF = 7.7 mW m −1 K −2 and Z = 1.5 mK −1 at 800 K, and the dimensionless value of Z T exceeds the criterion of 1. The PF and Z exceed the values of typical "high-temperature thermoelectric materials", such as p-type FeSi 2 and Si 0.7 Ge 0.3 . These results suggest that Na x CoO 2−δ could be a very promising material for use in high-temperature thermoelectric power generation devices.

The thermoelectric properties of Na,CoO,, single crystal have been evaluated at high temperatures (300 < T < 800 K) for the first time. The Na,CoO,, single crystals are prepared by a flux technique, and the flaky single crystals are very thin on the c-axis. The in-plane electrical resistivity (p), the thermoelectric power (S) and the in-plane thermal conductivity ( K ) are measured in the range of 300 K to 800 K. The estimated power factor (PF = S'*p-') and the figure-ofmerit (Z = S'.g'K") are about 2.4 mWrn-'Ke2 and 0.12 mK-' at 300 K, respectively. These factors increase with temperature, and reach the value of PF = 7.7 mWm-'K2 and Z = 1.5 m K ' at 800 K, and the dimensionless value of ZT exceeds the criterion of 1. The PF and Z exceed the values of typical "high temperature thermoelectric materials". These results suggest that Na,CoO,, could be a very promising material for use in the high-temperature thermoelectric power generation devices.

No abstract

No abstract

No abstract