An orange-emitting phosphor via the efficient Ce3+–Mn2+ and Eu2+–Mn2+ energy transfers in La9.33(SiO4)6O2 for UV or near-UV LEDs

Abstract

An orange-emitting phosphor was obtained via efficient Ce³⁺–Mn²⁺ and Eu²⁺–Mn²⁺ energy transfers in La_9.33(SiO₄)₆O₂, and has been developed for solid state UV/near-UV white lighting applications. The luminescence properties and energy transfer from Ce³⁺ to Mn²⁺ and Eu²⁺ to Mn²⁺ are investigated. The La_9.33(SiO₄)₆O₂:Ce³⁺, Mn²⁺ phosphor shows a blue emission centered at 380 and an orange emission peaking at 590 nm, which could be ascribed to the allowed 5d → 4f transition of the Ce³⁺ ion and the ⁴T_1g(4G) → ⁶A_1g(6S) transition of the Mn²⁺ ion, respectively. Upon excitation at 365 nm, the Eu²⁺, Mn²⁺ co-doped La_9.33(SiO₄)₆O₂ phosphor exhibits the Eu²⁺ green emission band and the Mn²⁺ orange emission band. Non-radiative transitions between the Ce³⁺/Eu²⁺ and Mn²⁺ ions in the La_9.33(SiO₄)₆O₂ host are both demonstrated to be attributable to dipole–quadrupole interactions. The intensity ratio of the Mn²⁺ emission bands can be enhanced through the increase of the Mn²⁺ content, which is attributed to the efficient energy transfer from Ce³⁺/Eu²⁺ to Mn²⁺, and the corresponding chromaticity coordinates (0.50, 0.38), (0.51, 0.46) were obtained with the La_9.33(SiO₄)₆O₂:Ce³⁺, Mn²⁺ and La_9.33(SiO₄)₆O₂:Eu²⁺, Mn²⁺ samples. Results indicated that the as-prepared phosphors might have promising applications in white-light LEDs as an orange-emitting phosphor.