Reducing particle size of persistent luminescent SrAl_2O_4:Eu^2+,Dy^3+via microwave-assisted, reverse micelle synthesis

Abstract

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 solution-based reverse micelle microemulusion synthesis route combined with rapid microwave-assisted 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.