Crystallinity and Luminescence of Strontium Aluminates for Digital Optical Data Storage Using NIR Excitation

Stably luminescent strontium aluminates (SAO) co-doped with Eu²⁺ and Dy³⁺ were synthesized by a solid-state reaction for digital optical data storage applications. The SAOs were composed of monoclinic SrAl₂O₄ and hexagonal SrAl₁₂O₁₉ in nearly identical composition ratios. The substitution of Dy³⁺ for Sr²⁺ decreased the high binding energy components of Sr 3d and Al 2p while decreasing the phosphor luminescence. However, co-doping with Dy³⁺ improved the persistent luminescence of Eu²⁺. When the phosphor was heated to 110°C, the luminescence intensity decreased by only 10.6%. Further, no change in the emission color was noted when the phosphor was placed in water and heated at 50°C for 20 min. The luminescence intensity of the phosphor changed with the switching of the optical stimulation; the higher the switching frequency, the better the optical storage performance. This indicates the promise of the polymorph SAO:Eu²⁺, Dy³⁺ for digital optical data storage applications utilizing near-infrared excitation.