Effect of Addition of Boron on the Long Afterglow Property of SrAl<sub>2</sub>O<sub>4</sub>: Eu<sup>2+</sup>, Dy<sup>3+</sup> Phosphor

The effect of addition of boron on the long afterglow property of SrAl2O4: Eu2+, Dy3+ by preparing the phosphors at various amount and types of boron compounds as flux was investigated. The addition of boron compounds as flux improved the long afterglow property and the sample with addition of H3BO3 showed higher afterglow intensity than that with addition of B2O3. The investigation of long afterglow property of the samples with various amounts of addition of H3BO3 revealed that there is a distinct correlation between afterglow intensity and boron content in the samples. Molar ratio of Sr4Al14O25 phase increased and unit cell volume of SrAl2O4 crystal decreased with an increase in the amount of addition of H3BO3. The result indicated that the substitution of BO4 for AlO4 in SrAl2O4 crystal phase promoted both incorporation of Dy3+ ions, which could act as electron traps, into Sr2+ sites and formation of strontium vacancies, which could act as hole traps, and then afterglow property of the phosphors was enhanced.