Investigation of local structure distortion and electron cloud interaction on emission-band broadening induced by the concentration perturbation effect of cation substitution in BaY2Si3O10:Eu phosphors

Abstract

The appearance of a cyan cavity is unavoidable in the 480–520 nm wavebands when combining n-UV LED chips (380–420 nm) with trichromatic phosphors to obtain white-light-emitting devices. Here, a concentration perturbation effect is proposed to improve the properties of phosphors via trace substitution of Mn²⁺, Mg²⁺ or Zn²⁺ cations for Ba²⁺ and Y³⁺ in Ba_0.97Y₂Si₃O₁₀:Eu. Based on local structure distortion or electron cloud interaction, the emission band corresponding to Eu²⁺ is broadened with a full width at half maximum (FWHM) more than 125 nm due to redistribution of Eu²⁺ and the emission color can be tuned to the cyan region. The coexistence of the above two effects on the photoluminescence can be further evidenced by the shifts of emission energy for the two sites in these systems. The quenching temperature for all the samples is observed over 473 K and even higher than that for the non-substituted Ba_0.97Y₂Si₃O₁₀:0.03Eu and it is discussed combined with Pauling's principles, average U_iso and the distortion degree of polyhedra, which could provide some references for improvement of thermal stability. Moreover, the valence mismatch between Mn²⁺/Mg²⁺/Zn²⁺ and Y³⁺ ions leads to the coexistence of Eu²⁺–Eu³⁺, which thus realizes color selective manipulation and even white light emission in Ba_0.98−nMg_0.02Y₂Si₃O₁₀:nEu. Our results demonstrate that the concentration perturbation effect-assisted synthesis strategy has potential in improving the properties of phosphors for WLEDs, and it can also be extended to adjusting the coordination environment of activators whose properties are sensitive to local lattice variations and electronic surroundings.