SrAl

2

O

4

:Eu

Dy is a new kind of attractive long-persistent luminescent material with green afterglow. It is necessary to make clear the mechanism of long-persistent luminescence of SrAl

2

O

4

:Eu

Dy. This paper was to investigate the effect of powder size on the luminescence of the material. In this work

SrAl

2

O

4

:Eu

Dy were made by heating at 1 350℃ for 5 hours in a reducing atmosphere of carbon powders.Then the blocks of SrAl

2

O

4

:Eu

Dy were milled into powders and separated by sieves with mesh numbers of 100

200

300

400 and 500

respectively. Also the powders sieved with 500 mesh were further separated by alcohol floatation method. Some white powders with very fine size can be removed from the green powders by alcohol floatation. It was found that the luminescent strength of the powders would decrease when their size become smaller. Among these powders the one separated by 100 mesh sieve has the strongest luminescence. The luminescence of the fine white powders separated by alcohol floatation is very poor

and the rest of the green powders will have better luminescence than that without alcohol floatation. The emission peak position in emission spectrum will not move due to powders size

but the excitation peak position in the excitation spectrum moved towards to short wave length when the powders become smaller. SEM and EDS experiments were carried out to study the size and chemical component of the powders. The white powders have a size of 1~2μm and the green powders have a size of about 20μm after alcohol floatation. In the green powders

Eu component is equal to or more than Dy component. However

in the white powders

Eu component is less than Dy component. It is reasonable to consider that too much Dy caused the luminescence decrease in the white powders.