Variations in the 5D0 → 7F0–4 transitions of Eu3+ and white light emissions in Ag–Eu exchanged zeolite-Y

Abstract

The variations in the ⁵D₀ → ⁷F_J(J=0–2) transitions of Eu³⁺ in the 580–630 nm range can reveal the exchanged-ion distribution within the zeolite pores for Ag–Eu exchanged zeolite-Y. A laser could excite more Eu³⁺ ions at symmetric sites (SI, SU) in the cages deep inside the zeolite besides activating those at the shallow surface. Significantly, the ⁵D₀ → ⁷F₄ transition of Eu³⁺ at 696 nm can be selectively modulated and enhanced by laser beam compared to xenon light according to the intensity ratio and decay-lifetime ratio of ⁵D₀ → ⁷F₄ to ⁵D₀ → ⁷F₂ transitions, which could be ascribed to the dynamic coupling effect on Eu³⁺ for the polarization of Eu³⁺-coordinated chemical environment induced by laser. Both transitions are determined by the odd-rank static electric field parameters of Eu³⁺ site according to the point charge model, but the ⁵D₀ → ⁷F₄ transition is further influenced by the polarizability of chemical environment around Eu³⁺ following the covalent bond model. Such strengthened effect may be partially relevant to the electronegativity of the zeolite framework. White light emission is achieved in these composites for excitation of both the 266 nm xenon lamp and laser, while the latter shows better tuning behaviors. The Ag–Eu codoped zeolite composites have potential applications in white light illumination.