On image phosphor degradation mechanism: thermal treatment effects

Fluorescence characteristics degradation mechanisms of plasma display panels (PDP) phosphor during panel fabrication and during panel life are not yet fully clarified. We present here the mechanism of luminance decrease in blue-emitting image phosphor due to the baking process, one step of the panel fabrication. It was shown experimentally that annealing in air leads to the oxidation of the dopant. It was demonstrated that during the oxidation process the decrease of divalent europium concentration is followed by an increase in the trivalent europium concentration but also by a decrease in the traps concentration. Based on these results and a numerical simulation, we proposed a model of the oxidation process. The degradation is due to three different mechanisms: the adsorption of an oxygen atom of the atmosphere into an oxygen vacancy of the surface phosphor, the diffusion of divalent europium ions along the conduction layer of BAM and the transfer of one electron from dopant ions to adsorbed oxygen ions when the divalent europium ions are close to adsorbed oxygen ions. We also develop two different solutions to stop or to minimize the degradation due to the baking process.