A structural approach of the flux effect on blue phosphor BAM:Eu (BaMgAl10O17:Eu2+)

• Effects of three fluoride fluxes on structural and spectroscopic properties of BAM:Eu2+ phosphor are studied.
• Flux recrystallization results in modifications of the dopant's distribution between host sites.
• Photoluminescence is strongly enhanced by LiF, in particular in the domain of excitation of near-UV LEDs.

In the aim of understanding the relations between the spectroscopic properties of blue phosphor BaMgAl10O17:Eu2+ and its crystal structure, microstructure and chemical composition, three fluoride fluxes (LiF, MgF2 and NH4F) have been added before final thermal treatment and their effect analyzed. LiF changes the polycrystalline and spherical grains into hexagonal platelets without significant cations exchange and improves the luminescence. NH4F and MgF2 only have a limited effect, the former because of its low point of decomposition, the latter because of the formation of spurious MgAl2O4 that reduces the luminescence. In a general way, re-crystallization results in variations of the dopant distribution between the three host sites of the structure. Chromaticity is only faintly affected, but important variations of the absorption and excitation spectra are observed, allowing a strong increase of photoluminescence intensity under near-UV excitation.

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