Thermoelectric oxide NaCo2O4 nanofibers fabricated by electrospinning

For the first time, sodium cobalt oxide (NaCo2O4) nanofibers with diameter of ∼20–200 nm were prepared by electrospinning a precursor mixture of sodium acetate/cobalt acetate/PAN, followed by calcination treatment of the electrospun composite nanofibers. The sodium cobalt oxide nanofibers were characterized by TG–DTA, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The NaCo2O4 nanofibers calcined at 300 and 400 °C were polycrystalline of γ-NaxCo2O4 phase having diameters of ∼20–60 nm with grain sizes of ∼5–10 nm, and whereas the nanofibers calcined at 800 °C were single crystal having linked particles or crystallites with particle sizes of ∼60–200 nm. The results indicated a significant effect of calcination temperature on the crystalline phase and morphology of the nanofibers.