Abstract
A series of five bulk samples of NaxCo2O4-yFy (x = 1.6, y = 0 to 0.20) compounds was successfully synthesized by employing the solution precursor method using CH3COONa, Co(CH3COO)2 and NaF dissolved in aqua regia. The XRD study with the Rietveld analysis revealed that the lattice parameter a slightly decreased with increasing F content y, while the c increased with increasing y. The electrical conductivity (sigma) of the compounds continuously decreased with increasing y. The See beck coefficient (S) once increased from y = 0 to 0.1 0, and decreased above y = 0.15. No improvement in the power factor (S2sigma) was observed in the compositional range of 0 L.T. y L.T. 0.20. The carrier concentration was unchanged over the compositional range of 0 L.T. y L.T. 0.20. A drastic reduction in the thermal conductivity (K) of the compounds was observed by substituting O atoms with F atoms at the anion site in the Na1.6Co2O4 compounds.
