Synthesis and luminescence properties of novel Eu2+/3+, Ce3+ ion single- and co-doped BaZn2(PO4)2 phosphors for white-light applications

Abstract

A series of novel Eu^2+/3+, Ce³⁺ ion single- and co-doped BaZn₂(PO₄)₂ samples were prepared via a high-temperature solid-state reaction. XRD powder diffraction results indicated that all of the products were pure phases. The photoluminescence properties of BaZn₂(PO₄)₂:Eu showed that Eu²⁺ and Eu³⁺ coexist in the system and Eu³⁺ can be self-reduced to Eu²⁺ in an air atmosphere. In addition, the strongest emission peak of Eu³⁺ ions at 593 nm implied that Eu³⁺ ions occupy the inversion symmetry lattice and also the site of Zn in BaZn₂(PO₄). We used the theoretical method of bond energy to explain why the self-reduction of Eu³⁺ to Eu²⁺ can occur in the BaZn₂(PO₄)₂ system. The calculation results indicated that the bond energy change value is smaller than , indicating that Eu²⁺ ions are more likely to occupy the Zn site and more stable than Eu³⁺ ions in BaZn₂(PO₄). Furthermore, the energy transfer process between Ce³⁺ and Eu²⁺ ions in the photoluminescence spectrum and the decay lifetime were observed, and the energy transfer mechanism was determined to be a dipole–dipole interaction. In this work, by adjusting the ratio of Ce and Eu ions, the emission color can be changed from blue to white, implying that the phosphor can be used as a promising candidate in the manufacture of white LEDs.