Facile synthesis of monodisperse SrAl2O4:Eu2+ cage-like microspheres with an excellent luminescence quantum yield

Abstract

Commercial LED phosphors are usually prepared by a conventional solid-state reaction method and a subsequent ball milling process, which often results in non-uniform size distributions, irregular shape and impurity contamination of the phosphors. In this work, the SrAl₂O₄:Eu²⁺ cage-like microspheres with a uniform size distribution and excellent photoluminescence (PL) quantum yield (QY) are prepared by an epoxide-driven sol–gel route and subsequent heat treatment in a reducing atmosphere. This unique cage-like microstructure not only makes better use of the excited light but also significantly increases the PL quenching concentration of the Eu²⁺ ions. The optimum internal QY of the SrAl₂O₄:Eu²⁺ cage-like microspheres is measured to be up to 94.94%, much higher than the highest internal QY (55%) of the SrAl₂O₄:Eu²⁺ phosphors reported so far. The approach may be readily applied to prepare other lanthanide ions doped cage-like microspheres, implying a new route for preparing highly efficient PL phosphors with regular shape and uniform particle size.