Preparation and characterization of orange-yellow emitting Li2Ca0.4Sr0.6SiO4:Eu2+, Dy3+ phosphor with afterglow behavior

Orange-yellow emitting long afterglow phosphors Li2Ca0.4Sr0.6SiO4:Eu2+, and Li2Ca0.4Sr0.6SiO4:Eu2+,Dy3+ were synthesized via a high temperature solid-state reaction in a reducing atmosphere (N2:H2=95:5). X-ray diffraction (XRD), photoluminescence spectroscope (PLS), long afterglow spectroscope (LAS), thermal luminescence spectroscope (TLS) were performed to characterize the physical properties of the prepared phosphors. Typical 4f65d1→4f7 transitions of Eu2+ ions were detected by PL spectra, revealing a broad and intensive emission extending from 500 to 700 nm with a peak at about 587 nm, corresponding to CIE chromaticity coordinates of x=0.5368, y=0.4593, in the orange-yellow region. Optimal concentrations of Eu2+ and Dy3+ in the substrate were determined as 7 at% and 3 at%, respectively. The prepared phosphors showed a typical afterglow behavior when the UV source was switched off. Typical triple exponential decay behaviors were confirmed after fitting the experimental data for both samples. Thermal simulated luminescence study further indicated that the enhancement of afterglow property of Li2Ca0.4Sr0.6SiO4:Eu2+, Dy3+ phosphor was due to the increased trap concentration resulting from the incorporation of Dy3+ ions. The afterglow mechanism of Li2Ca0.4Sr0.6SiO4:Eu2+, Dy3+ is illustrated and discussed in detail on the basis of experimental results.