Photoluminescence degradation and color shift studies of annealed BaMgAl10O17:Eu2+ phosphor

The photoluminescence (PL) in UV and VUV regions, such as excitation and emission spectra, PL intensity, full-width at half-maximum (FWHM) and chromaticity coordinates, of pre- and post-annealed BaMgAl10O17:Eu2+ (BAM) samples were investigated. The observed more PL degradation under VUV excitation was assigned to the formation of defects (extinction centers or new Eu2+ centers) which decreased the luminance efficiency of Eu2+ in mirror plane. The increasing y value of chromaticity coordinates that appeared in annealed samples under 147 nm excitation was attributed to the migration of Eu2+ from mirror plane to spinel block, which induced long wavelength emission. Therefore, besides the well-accepted oxidation mechanism, the migration of Eu2+ also led to the decrease of blue luminescent centers, and there by is responsible for the PL degradation, too. The conclusion of this work revealed a more full-scale and precise mechanism of thermal degradation than the conventional one.