Synthesis and luminescence properties of novel Eu 2+/3+ , Ce 3+ ion single- and co-doped BaZn 2 (PO 4 ) 2 phosphors for white-light applications.

A series of novel Eu 2+/3+ , Ce 3+ ion single- and co-doped BaZn 2 (PO 4 ) 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 BaZn 2 (PO 4 ) 2 :Eu showed that Eu 2+ and Eu 3+ coexist in the system and Eu 3+ can be self-reduced to Eu 2+ in an air atmosphere. In addition, the strongest emission peak of Eu 3+ ions at 593 nm implied that Eu 3+ ions occupy the inversion symmetry lattice and also the site of Zn in BaZn 2 (PO 4 ). We used the theoretical method of bond energy to explain why the self-reduction of Eu 3+ to Eu 2+ can occur in the BaZn 2 (PO 4 ) 2 system. The calculation results indicated that the bond energy change value is smaller than , indicating that Eu 2+ ions are more likely to occupy the Zn site and more stable than Eu 3+ ions in BaZn 2 (PO 4 ). Furthermore, the energy transfer process between Ce 3+ and Eu 2+ 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.