Cathodoluminescence study of novel sol–gel derived Y3−xAl5O12 : Tbx phosphors

The synthesis, physical characterization and cathodoluminescence (CL) of sol–gel derived Y3−xAl5O12 : Tbx3+ (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°C the non-crystalline xero–gel fully crystallized to form the single-phase YAG powder. The powder X-ray diffraction showed that the garnet structure and all reflections were indexed without any other secondary impurity phases. From the CL spectrum, all possible transitions 5D4→7F1…6 due to Tb3+ in YAG structure were identified including the bright green emission at 548 nm. The highest luminance at a fixed beam current density was observed for the Tb concentration of x=0.12 (4% atomic). The CL intensity increased linearly with current densities from 1 to 60 μA/cm2 but remained nearly constant from 60 to 100 μA/cm2. Two exponentially decaying functions that were fitted to the pulsed-CL decay curve illustrated the emission decay from 5D4 and 5D3 to 7FJ levels with their characteristic lifetimes. Both CL luminance and the decay time are comparable with commercially available optimized phosphors used for CRT and FED applications.