Synthesis and Properties of Boron Doped Na_xCo₂O₄ Nanocrystalline Ceramics

Abstract

Sodium cobalt oxide (NaCo₂O₄) nanofibers with diameters ranging between 20 and 200 nm were prepared by electrospinning a precursor mixture of PVA/(Na–Co) acetate. This was the first time any such attempt was made. Afterwards, the electrospun nanofibers were subjected to calcination treatment. The characteristics of the fibers were investigated using a Fourier transform infrared spectroscopy, a X-ray diffractometer, and a scanning electron microscopy. The boron doped and undoped NaCo₂O₄ nanofibers calcined at 850 °C were polycrystalline of the γ Na_xCo₂O₄ phase having diameters ranging between 20 and 60 nm with grain sizes of 5–10 nm, and the nanofibers calcined at 800 °C were single crystals having linked particles or crystallites with particle sizes ranging between 60 and 200 nm. The results indicated a significant effect of calcination temperature on the crystalline phase and morphology of the nanofibers. It could be seen in the SEM micrograph of the fibers that when boron was added, this resulted in the formation of cross-linked bright-surfaced fibers. The average fiber diameter for boron doped and undoped fiber mats were 204 and 123 nm, respectively. The grain diameters of boron doped and undoped nanocrystalline sintered powders were measured as 140 and 118 nm, respectively.