Influence of partial substitution of Cu for Co on the thermoelectric properties of NaCo 2O 4

Abstract

Cu-substituted Na(Co 1− y Cu y ) 2O 4 (0 ≤ y ≤ 0.2) polycrystalline samples have been prepared using a solid-state reaction method and their thermoelectric properties studied. The electrical conductivity of Na(Co 1− y Cu y ) 2O 4 decreased with increasing temperature, indicating metallic behavior. The electrical conductivity ( σ) of Cu-substituted Na(Co 1− y Cu y ) 2O 4 was much higher than that of Cu-free NaCo 2O 4. In addition, the Seebeck coefficient ( α) of Na(Co 1− y Cu y ) 2O 4 increased with increasing temperature and the Cu substitution led to an increase in the Seebeck coefficient. The power factor ( σα 2) increased with an increase in temperature and the highest value of power factor (3.08 × 10 −3 W m −1 K −2) was attained for Na(Co 0.9Cu 0.1) 2O 4 at 1073 K. We demonstrate that the Cu substitution is effective for enhancing thermoelectric properties.