Photoluminescence of titanium-doped zinc spinel blue-emitting nanophosphors

A blue-emitting phosphor of titanium-doped zinc spinel (ZnAl2O4:Ti; Ti=0-6.0 mol% in relation to Al) nanopowders was prepared by a simple sol-gel method. On annealing at 1000 degrees C, single-phase ZnAl2O4:Ti powders had primary particles of 25-30 nm in size and most Ti ions in the form of Ti4+. Under UV excitation at 280 nm, a strong and broad blue emission centered at 435 nm was observed. The sources of the excitation and emission were assigned to the charge-transfer excitation and recombination between O2--Ti4+ and Ti3+-O- ion pairs. Optimum brightness occurred at a doping of 2.0 mol% Ti. The decay lifetime of ZnAl2O4:2%Ti was calculated to be 3.0 ms for the blue emission with CIE coordinates of x=0.168 and y=0153. The results suggest that ZnAl2O4:Ti is a promising candidate for application as a blue component phosphor for UV-converting white light-emitting diodes. (C) 2013 Elsevier Inc. All rights reserved.