Luminescence quenching in thermally-treated barium magnesium aluminate phosphor

Abstract

${\mathrm{BaMgAl}}_{10}{\mathrm{O}}_{17}:{\mathrm{Eu}}^{\text{2+}}$ (BAM) phosphors used for plasma display panels (PDP) are compelled to be exposed to an oxidizing environment at about 500 °C, which is currently unavoidable in the actual manufacturing process of PDP. We investigated the mechanism of the luminance degradation of BAM caused by the annealing at 500 °C, using photoluminescence (PL), decay measurement, and synchrotron light source x-ray absorption and diffraction measurements. The annealing treatment altered the valence state of Eu ions, whereas no new Eu compounds were detected. By estimating the exact fraction of divalent Eu ions and by comparing it with the luminance data, we found that more than 30% degradation of luminance was induced at the expense of only a few percent of divalent Eu. This finding led us to suggest that the origin of the dramatic decrease in PL intensity is not due to the valence state change but due to the local structure change surrounding the ${\mathrm{Eu}}^{\text{2+}}$ ions.