Aqueous degradation and atomic layer deposition (ALD) stabilization of BaAl2O4: Eu2+, Dy3+long afterglow phosphors

This paper presents the aqueous degradation mechanisms of BaAl2O4:Eu2+, Dy3+ phosphors and demonstrates an ability to prevent degradation via Al2O3 nano encapsulation of powders by atomic layer deposition (ALD) technique. Phosphor powder is synthesized from the solid-state reaction method. The aqueous degradation of this phosphor is systematically studied. This phosphor is found to hydrolyze and degrade within just 30 min of exposure in water. The degradation of BaAl2O4 host lattice directly affects the blue-green light emission at 497 nm, producing blue-and red-emissions that are peaked at 429 nm and 687 nm, respectively. Hydrated and structural decomposed BaAl2O4 reveals a continuous change in the phase assemblage over 30 days of immersion. To prevent this rapid degradation, use of a protective nanocoating was investigated. 10 nm Al2O3 coatings were applied to the surface of the phosphor powder via ALD. ALD coated BaAl2O4:Eu2+,Dy3+ phosphor retains its phosphorescence for at least 7 days of water exposure. Successful encapsulation of such phosphor particles will make them possible to use in aqueous applications or store in long-term humid environments.

Automated summary

This paper presents the mechanisms of aqueous degradation of BaAl2O4:Eu2+, Dy3+ phosphors and proposes a method to prevent degradation by nano encapsulation with Al2O3 through atomic layer deposition (ALD) technique. The degradation behavior of the phosphor in water is systematically studied, revealing hydrolysis and structural decomposition. A protective nanocoating using 10 nm Al2O3 is found to effectively prevent degradation for at least 7 days of water exposure. Successful encapsulation enables the potential use of the phosphor in aqueous applications or long-term humid environments.