Size dependence of the luminescence spectra of nanocrystal alumina

A nanometer-sized Al₂O₃ powder was prepared by calcination of the nanometer-sized boehmite powder at different temperatures for 3 h in air. The main absorption bands located at about 200, 236, 255, 334 and 348 nm always occur in any phase of nanometer-sized alumina powder, and also do not change with the particle size. The luminescence bands at 404 nm in nanometer-sized alumina powder are presented under 236 and 254 nm excitation, respectively. The luminescence intensity of peak located at 404 nm decreases quickly with the increasing alumina powder size. It is suggested that the defect level in the nanometer alumina powder should be taken into account for the mechanism of new luminescent emission bands.