  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.
