Understanding and arresting degradation in highly efficient blue emitting BaMgAl10O17:Eu2+ phosphor-A longstanding technological problem

Blue emitting BaMgAl10O17:Eu2+ (BAM) phosphor is indispensable for Plasma Display panel and lighting because of high luminescence efficiency. However, thermal degradation (annealing in air at 500-600 °C) of BAM (upto ∼30%) remains an intriguing problem for display industry worldwide. In the present study, a systematic approach is pursued to develop highly efficient BAM phosphor that exhibits least degradation, understand the role of Eu2+ site occupancy in such BAM phosphor and encapsulate individual phosphor grains with a shell of silica nanoparticles. The approaches lead to highly efficient BAM:Eu2+ phosphor that showed no degradation against thermal baking (annealing at 500 °C in air) for both UV and VUV radiation under UV and VUV excitation. An optimum solid state chemical route including precursor phases, dopant concentration, and thermal regimes has been evolved to develop BAM. Emission from Eu2+ occupying three different sites is identified with energetically stable anti Beevers Ross as the dominant contributor. Coating by nano sized amorphous silica sol with subsequent sintering lead to uniform silica shell. This nano silica layer also helps to enhance the luminescence from phosphor grains.