Fabrication of nanotubules of thermoelectric gamma-Na0.7CoO2 using porous aluminum oxide membrane as supporting template

We report the successful synthesis of nanotubules of thermoelectric materials gamma-NaxCoO2 using two different sol-gel routes aided by porous anodized aluminium oxide (AAO) membrane as supporting templates. The gamma-NaxCoO2 nanotubule using urea-based route can be achieved at 650 degree C at a heating rate of 1 degree C/min and held for 4h. The gamma-NaxCoO2 nanotubule using citric acid-based route can be achieved at 500 degree C using a rapid-heat-up procedure and held for 30 min. The products were investigated using various techniques including XRD, SEM and TEM. Electron diffraction pattern taken along [001] zone axis direction on the nanotubule shows that all the diffraction spots can be indexed using a hexagonal unit cell with a = b = 0.56 nm, which can be considered as a superstructure with cell doubling within the ab plane.