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

The preparation, structure and luminescence of the Ca1-xSrxAl2O4:Eu2☎, RE3☎ 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:Eu2☎ and hexagonal SrAl2O4:Eu2☎ ones. The persistent luminescence was enhanced by the Ca/Sr replacement. This observation supports the mechanisms where the lattice defects act as traps.