Luminescence properties and energy transfer behavior of colour-tunable white-emitting Sr4Al14O25 phosphors with co-doping of Eu2+, Eu3+ and Mn4+

Abstract

Eu²⁺, Eu³⁺ and Mn⁴⁺ co-doped Sr₄Al₁₄O₂₅ phosphors were synthesized in air by high temperature solid-state reaction. The coexistence of Eu²⁺, Eu³⁺ and Mn⁴⁺ in Sr₄Al₁₄O₂₅ was detected and verified from X-ray photoelectron spectra (XPS), photoluminescence (PL)/photoluminescence excitation (PLE) spectra and diffuse reflection spectra. The crystal structure, luminescence properties and energy transfer between Eu²⁺ and Mn⁴⁺ were investigated scientifically. Under ultraviolet excitation, a broad emission band with peak at 496 nm was ascribed to a 4f⁶5d–4f⁷ transition of Eu²⁺, and another five narrow emission bands were attributed to 4f–4f transitions of Eu³⁺. The sharp emission band with peak at 659 nm was generated from the spin-forbidden electronic transition ²E_g–⁴T₂ of Mn⁴⁺. The energy transfer between Eu²⁺ and Mn⁴⁺ was demonstrated following the nonradiative electric dipole–dipole interaction, and the energy transfer efficiency reached 58.16%. The emission colour of Sr₄Al₁₄O₂₅:Eu,Mn⁴⁺ can be tuned from blue-green (0.2396, 0.3332) to white (0.3465, 0.2906) with increasing concentrations of Mn⁴⁺.