Thermoelectric properties of NaCo2O4

The thermoelectric properties: such as the thermal conductivity, electrical resistivity and Seebeck coefficient of NaCo2O4, and NaCo1.9M0.1O4 (M=Ti, Rh, Pd) were evaluated in the temperature range from room temperature to 723 K. Polycrystalline samples were prepared by sintering in air followed by hot pressing. The thermal conductivity was calculated from the heat capacity, the experimental density, and the thermal diffusivity measured by the laser flash method, The electrical resistivity and Seebeck coefficient were measured simultaneously using ULVAC ZEM-1 in He atmosphere. The dimensionless figure of merit, ZT, of NaCo1.9Pd0.1O4 was higher than that of NaCo2O4 over a wide ranee of temperatures, and reached ZT = 0.045 at 773 K. (C) 2001 Elsevier Science B.V. All rights reserved.