Eu2+ → Tb3+ → Eu3+ energy transfer in Ca6La2Na2(PO4)6F2:Eu, Tb phosphors

Abstract

Novel phosphors Ca₆La₂Na₂(PO₄)₆F₂:0.10Eu²⁺/Eu³⁺, xTb³⁺ (x = 0, 0.05, 0.10, 0.20, 0.30, 0.40, 0.50) were prepared by a solid state reaction in a CO-reducing atmosphere. The fluorescence spectra of samples Ca₆La₂Na₂(PO₄)₆F₂:xEu²⁺ reveal that still a small number of Eu³⁺ ions are detected in the host. The Eu²⁺ → Tb³⁺ → Eu³⁺ energy transfer process in Ca₆La₂Na₂(PO₄)₆F₂:0.10Eu²⁺/Eu³⁺, xTb³⁺ phosphors was discussed in detail through the excitation, emission spectra and the fluorescence decay. As a result of Eu²⁺ sensitization, the relative emission intensity of Ca₆La₂Na₂(PO₄)₆F₂:0.10Eu²⁺/Eu³⁺, xTb³⁺ is enhanced under near-ultraviolet light excitation. Furthermore, tunable emission with a large color gamut can be obtained by changing the Tb³⁺ doping concentration. These results indicate that the Ca₆La₂Na₂(PO₄)₆F₂:Eu²⁺/Eu³⁺, Tb³⁺ phosphors will have potential use in n-UV chip pumped white LED devices.