Synthesis and Rietveld analysis of new thermoelectric oxides F-doped Na1. 6 Co204

A series of five bulk samples of NaxCo 2 0 4 .yFy (x = 1.6, y = 0 to 0.20) compounds was successfully synthesized by employing the solution precursor method using CH 3 COONa, Co(CH1C00)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 (a) 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 (S2 o-) was observed in the compositional range of 0 :S y :S 0.20. The carrier concentration was unchanged over the compositional range of 0 :S y :S 0.20. A drastic reduction in the thermal conductivity ( K) of the compounds was observed by substituting 0 atoms with F atoms at the anion site in the Na1. 6 Co20 4 compounds.