Potential color tunable Sr3LaNa(PO4)3F:Eu2+/Tb3+/Mn2+ phosphor induced by Eu2+ → Tb3+ and Tb3+ → Mn2+ energy transfer for WLEDs

Abstract

Color tunable Sr₃LaNa(PO₄)₃F:Eu²⁺,Tb³⁺ and Sr₃LaNa(PO₄)₃F:Tb³⁺,Mn²⁺ phosphors were prepared by a high temperature solid state reaction. The crystal structure, luminescence properties, and energy transfer mechanism of the samples were investigated in detail. The Eu²⁺ doped phosphors can be efficiently excited in the range from 250 to 410 nm, which matches well with the commercial n-UV LED chips. Utilizing the energy transfer from Eu²⁺ to Tb³⁺ ions, tunable colors from blue to green were obtained under the irradiation of 405 nm. The mechanism of the Eu²⁺ → Tb³⁺ energy transfer was demonstrated to be a dipole–quadrupole interaction in terms of the experimental results and analysis of the photoluminescence spectra and decay curves of the phosphors. Moreover, the thermal stability and quantum efficiency of the Eu²⁺ and Tb³⁺ co-doped phosphors were studied. For the Sr₃LaNa(PO₄)₃F:Tb³⁺,Mn²⁺ samples, tunable green-orange emissions were obtained by changing the relative ratio of Tb³⁺ and Mn²⁺ ions under 230 nm irradiation. The investigation results suggest that color tunable phosphors with potential for WLEDs were obtained utilizing the energy transfer process.