Reducing particle size of persistent luminescent SrAl₂O₄: Eu²⁺,Dy³⁺ via microwave-assisted, reverse micelle synthesis

The synthesis of persistent luminescent, monoclinic SrAl₂O₄:Eu²⁺,Dy³⁺ traditionally employs high temperature solid state methods, which tends to generate large particles and agglomerates (>15 μm). Alternatively, soft chemical synthetic routes are conducive to forming significantly smaller particles of SrAl₂O₄:Eu²⁺,Dy³⁺; unfortunately, many of the reported routes lead to impure products, including the presence of the hexagonal SrAl₂O₄:Eu²⁺,Dy³⁺ polymorph and Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺. Here, the combination of a solutionbased reverse micelle microemulusion synthesis route combined with rapid microwaveassisted heating is shown to produce nearly phase pure monoclinic SrAl₂O₄:Eu²⁺,Dy³⁺ with a ≈70% smaller equivalent spherical diameter (4.2 μm) compared to the all solid state prepared materials (14.3 μm). Optical characterization including photon excitation, photon emission, persistent luminescent lifetime, and thermoluminescence measurements support that the optical properties remain almost unchanged, regardless of synthetic route. These results validate that monoclinic SrAl₂O₄:Eu²⁺,Dy³⁺ produced using this pathway is viable as an alternative to the all solid state-prepared materials, with the added advantage of significantly smaller particles that may be desirable when architecting new potential applications.