Synthesis and photoluminescence properties of Ce3+ and Eu2+-activated Ca7Mg(SiO4)4 phosphors for solid state lighting

Abstract

Ce³⁺ and Eu²⁺ singly doped and Ce³⁺/Eu²⁺-codoped Ca₇Mg(SiO₄)₄ phosphors are synthesized by the conventional solid state reaction. The Ce³⁺ activated sample exhibits intense blue emission under 350 nm excitation, the composition-optimized Ca₇Mg(SiO₄)₄ : 4%Ce³⁺ shows better color purity than the commercial blue phosphor, BaMgAl₁₀O₁₇ : Eu²⁺ (BAM : Eu²⁺) and exhibits superior external quantum efficiency (65%). The Ca₇Mg(SiO₄)₄ : Eu²⁺ powder shows a broad emission band in the wavelength range of 400–600 nm with a maximum at about 500 nm. The strong excitation bands of the Ca₇Mg(SiO₄)₄ : Eu²⁺ in the wavelength range of 250–450 nm are favorable properties for applications as light-emitting-diode conversion phosphors. Furthermore, the energy transfer from the Ce³⁺ to Eu²⁺ ions is observed in the codoped samples, the resonance-type energy transfer is determined to be due to the dipole–dipole interaction mechanism and the critical distance is obtained through the spectral overlap approach and concentration quenching method.