Persistent Luminescence Features in Hexagonal Sr_1-x/2Al_2-xSi_xO₄:Eu²⁺,Dy³⁺ Compounds

Abstract

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.