Mechanisms of VUV Damage in BaMgAl10O17:Eu2+

We have studied vacuum ultraviolet (VUV)-induced damage processes in BaMgAl10O17:Eu2+ using a unique accelerated lifetesting device. Emission, excitation, and reflectance spectra of doped and undoped samples before and after VUV damage reveal two independent mechanisms of degradation. The observed color shift in damaged materials is due to the migration of Eu2 + ions to metastable sites in the lattice. The observed loss of brightness is due in part to the formation of color centers in the spinel layer that act as energy traps and also absorb the exciton emission of the host lattice, thus interrupting the transfer of energy from the host to the activator. Several modes of energy transfer to Eu2+ are available depending on the excitation energy.