Structure and photoluminescence properties of strong blue-emitting alumina film developed from a liquid sol at low temperature

Strong blue photoluminescence emission at 450 nm from alumina films prepared from an alumina precursor was observed. Photoluminescence measurements indicate that the peak intensity of the blue emission changes with the pH value of the peptizing solution, the annealing temperature and the atmosphere. The blue emission appears at a low temperature of 50 °C and reaches a maximum strength at 400 °C in an oxygen atmosphere and 600 °C in a nitrogen atmosphere. HRTEM images show that the alumina films are composed of nanoparticles with a diameter of ≦10 nm. It is believed that the observed strong photoluminescence is associated with inherent defect centers in the material, where these are related to the structure transition and transformation from the boehmite phase to the γ-alumina phase and bond cleavage.