CaAl2Si2O8:Dy3+, Eu3+: synthesis, luminescence properties, energy transfer, and tunable emission

Luminescent materials used in solid-state lighting usually face the challenge of the adjustment of luminescence properties. The coordinated luminescence of two activators in luminescent materials is a good method. Herein, CaAl2Si2O8:Dy3+, CaAl2Si2O8:Eu3+, and CaAl2Si2O8:Dy3+, Eu3+ with a pure phase (CaAl2Si2O8) were synthesized in air. The X-ray diffraction patterns of the samples were measured and their crystal structures were elucidated. Under excitation at 350 nm, the yellow emission of CaAl2Si2O8:Dy3+ in the spectral range of 525-800 nm was observed due to the F-4(9/2) -> H-6(15/2), H-6(13/2), H-6(11/2), and H-6(9/2) transitions of Dy3+ ions. CaAl2Si2O8:Eu3+ showed red emission in the range of 550-720 nm because of the transitions D-5(0) -> F-7(1), F-7(2), F-7(3), and F-7(4) of Eu3+ ions when it was excited by 394 nm light. A tunable color emission of CaAl2Si2O8:Dy3+, Eu3+ from yellow to red was found when the ratio between Dy3+ and Eu3+ ions was changed. We investigated the concentration-dependent spectra and ensured the optimal Dy3+ and Eu3+ concentrations in host CaAl2Si2O8. The spectra of the samples manifested the energy transfer from Dy3+ to Eu3+ ions. The energy-level diagrams of Dy3+ and Eu3+ ions were used to analyze the luminous mechanism of the samples. The research results are beneficial to the development of other Dy3+ and Eu3+ co-doped luminescence materials.