Thermoelectric properties of NaxCo2O4/Ag composites

Polycrystalline samples of NaxCo2−yAgyO4 (x ∼ 1.5, y = 0, 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized from powder precursors prepared by a polymerized complex (PC) method. The thermoelectric properties were evaluated in the temperature range from room temperature to 973 K. The electrical resistivity and Seebeck coefficient were measured simultaneously using ULVAC ZEM-1 in He atmosphere. The thermal conductivity was calculated from the heat capacity, density, and thermal diffusivity measured by the laser flash method using ULVAC TC-7000 in vacuum. The dimensionless figure of merit (ZT) of an Ag-doped (0.2) sample was higher than that of the non-doped sample, and reached ZT = 0.12 at 973 K.