In-air self-reduction synthesis and photoluminescent properties of Eu2+-Eu3+ activated CaAl2SixO2x+4 phosphors

In this paper, CaAl2SixO2x+4:Eu2+/Eu3+ (2%, molar ratio) phosphors with different SiO2 concentrations (x=0, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 1.5, and 2) were prepared by a high-temperature solid-state reaction under air condition with the absence of the reduction atmosphere. The crystalline phase, photoluminescent properties and luminescent lifetimes of the prepared samples were systematically studied. The results indicated that Eu2+ was reduced and obtained in air through self-reduction. The doping of SiO2 in calcium aluminates strongly affects the crystalline phase, excitation and emission spectra, CIE (Commission Intemationale de I'Eclairage 1931 chromaticity) (x, y) position and lifetimes of europium. It is interesting and important that different luminescent colors can be obtained and modulated by changing the content of SiO2.