Structure and photoluminescence characteristics of europium(iii) doped in CaAl2Si2O8 phosphors

Abstract

A series of Eu³⁺ activated CaAl₂Si₂O₈ phosphors have been synthesized at 1350 °C in air, and their photoluminescence properties have been investigated as a function of activator concentrations. The results show that the dominant emission peak of the phosphors Ca_1−3x/2Al₂Si₂O₈:xEu³⁺ is located at ∼611 nm due to Eu³⁺ transition (⁵D₀ → ⁷F₂). The reduction reaction from Eu³⁺ to Eu²⁺ is observed by the luminescent spectra because of the charge compensation mechanism and the special structure of the CaAl₂Si₂O₈ host lattice even when synthesized in air. The energy transfer rate between the Eu³⁺ pairs is not very high as proved by the results of the decay lifetimes and the efficiency of Eu^{3+ 5}D₀ → ⁷F₂ emissions. The thermal quenching behaviour is attributed to the crossover process from the ⁵D₀ to the charge transfer state (Eu³⁺–O²⁻) band. The CIE chromaticity coordinates of the red emission of the Ca_0.925Eu_0.05Al₂Si₂O₈ phosphor is (0.59, 0.28), which is the NTSC system standard for red chromaticity. With enhanced properties (i.e., colour render property) and the ability to be efficiently stimulated by NUV and blue UV LEDs, this kind of phosphor can be used in developing novel types of flat panel and projection displays.