Spectroscopic and Structural Properties of Ca1-xSrxAl2O4:Eu2☎, RE3☎Persistent Luminescence Materials

Abstract

The preparation, structure and luminescence of the Ca_1-xSr_xAl₂O₄:Eu^2☎, RE^3☎ system were studied. Monoclinic CaAl₂O₄ was the major phase when the strontium content x was from 0 to 0.6, but hexagonal SrAl₂O₄ was obtained when x was 0.8 and monoclinic SrAl₂O₄ when x was 1. Only slight Ca/Sr cation solid solubility was observed. The strontium ions dissolved better into the CaAl₂O₄ phase than vice versa. Two luminescence bands were observed for mixed compositions, peaking at 440 and 530 nm, corresponding to those of the monoclinic CaAl₂O₄:Eu^2☎ and hexagonal SrAl₂O₄:Eu^2☎ ones. The persistent luminescence was enhanced by the Ca/Sr replacement. This observation supports the mechanisms where the lattice defects act as traps.