Growth and characterization of ceria thin films and Ce-doped γ - Al 2 O 3 nanowires using sol-gel techniques

Abstract

γ - Al 2 O 3 is a well known catalyst support. The addition of Ce to γ - Al 2 O 3 is known to beneficially retard the phase transformation of γ - Al 2 O 3 to α - Al 2 O 3 and stabilize the γ-pore structure. In this work, Ce-doped γ - Al 2 O 3 nanowires have been prepared by a novel method employing an anodic aluminium oxide (AAO) template in a 0.01 M cerium nitrate solution, assisted by urea hydrolysis. Calcination at 500 °C for 6 h resulted in the crystallization of the Ce-doped AlOOH gel to form Ce-doped γ - Al 2 O 3 nanowires. Ce 3 + ions within the nanowires were present at a concentration of < 1 at.%. On the template surface, a nanocrystalline CeO 2 thin film was deposited with a cubic fluorite structure and a crystallite size of 6–7 nm. Characterization of the nanowires and thin films was performed using scanning electron microscopy, transmission electron microscopy, electron energy loss spectroscopy, x-ray photoelectron spectroscopy and x-ray diffraction. The nanowire formation mechanism and urea hydrolysis kinetics are discussed in terms of the pH evolution during the reaction. The Ce-doped γ - Al 2 O 3 nanowires are likely to find useful applications in catalysis and this novel method can be exploited further for doping alumina nanowires with other rare earth elements.