Effect of nominal substitution of Dy3+ for host cations in SrAl2O4: Eu2+ phosphor on phase evolution and long afterglow luminescence

SrAl2O4: Eu2+, Dy3+ long-afterglow (LAG) phosphors with nominal substitution of Dy for Al site demonstrated superior performance as compared to the cases of nominal substitution for the Sr site or excess addition, despite the fact that a reduced quantity of the SrAl2O4 main host phase existed when Dy3+ was nominally substituted for Al. It was deduced that if the number of Al available for the formation of the main host was less than the stoichiometric value of 2 with reference to the number of Sr lattice site in the main host, boron would suitably join the [Al,B]O4 structural unit, yielding an improved incorporation of Dy3+ to the SrAl2O4 main host which, in turn, improves the LAG luminescence.