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

Abstract

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 ⁴F_9/2 → ⁶H_15/2, ⁶H_13/2, ⁶H_11/2, and ⁶H_9/2 transitions of Dy³⁺ ions. CaAl₂Si₂O₈:Eu³⁺ showed red emission in the range of 550–720 nm because of the transitions ⁵D₀ → ⁷F₁, ⁷F₂, ⁷F₃, and ⁷F₄ 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.