Persistent Luminescence Features in Hexagonal Sr1-x/2Al2-xSixO4:Eu2+,Dy3+ Compounds

Rare earth doped aluminates, such as SrAl
2
O
4
:Eu
²⁺
,Dy
³⁺
and CaAl
2
O
4
:Eu
²⁺
,Nd
³⁺
, are among the best known materials for persistent luminescence or afterglow emission [1]. Numerous studies have been carried out on this strontium aluminate to find different elaboration ways and to elucidate its persistent luminescence mechanism (see for instance [2]). It recently appeared that its hexagonal phase polymorph, which is not stable at room temperature, could have promising properties. A recently efficient way to elaborate the hexagonal Sr
1-x/2
Al
1-x
Si
x
O
4
: Eu
²⁺
,Dy
³⁺
phases has been developed by glass crystallization. We report here the optical features of Eu
²⁺
, Dy
³⁺
co-doped Sr
1-x/2
Al
1-x
Si
x
O
4
(0 ≤ × ≤ 0.6) powders elaborated by this method. The experimental results show that the photoluminescence as well as the afterglow emissions shift from green to white/blue range as x increases (see Fig. 1-left). This color change toward the white color is due to two effects: the blue shift of Eu
²⁺
broad emission and the appearance of Dy
³⁺
emission.