Cathodoluminescence study of novel sol-gel derived Y3-xAl5O12 : Tb-x phosphors

The synthesis, physical characterization and cathodoluminescence (CL) of so l-gel derived Y3-xAl5O12:Tb-x(3+) (YAG, x = 0.03-0.15) powders is presented . Metal-alkoxide organic precursors were used as the starting materials to form the sol-gel with the required stoichiometry. At a temperature between 900 and 950 degreesC the non-crystalline xero-gel fully crystallized to for m the single-phase YAG powder. The powder X-ray diffraction showed that the garnet structure and all reflections were indexed without any other second ary impurity phases. From the CL spectrum, all possible transitions D-5(4) --> F-7(1...6) due to Tb3+ in YAG structure were identified including the b right green emission at 548 nm. The highest luminance at a fixed beam curre nt density was observed for the Tb concentration of x = 0.12 (4% atomic). T he CL intensity increased linearly with current densities from 1 to 60 muA/ cm(2) but remained nearly constant from 60 to 100 muA/cm(2). Two exponentia lly decaying functions that were fitted to the pulsed-CL decay curve illust rated the emission decay from D-5(4) and D-5(3) to F-7(J) levels with their characteristic lifetimes. Both CL luminance and the decay time are compara ble with commercially available optimized phosphors used for CRT and FED ap plications. (C) 2001 Elsevier Science B.V. All rights reserved.