Energy transfer induced improvement of luminescent efficiency and thermal stability in phosphate phosphor

Ce³⁺ and Eu²⁺/Tb³⁺/Mn²⁺ ions codoped Ca₆BaP₄O₁₇ (CBPO) phosphors have been prepared via a high-temperature solid state reaction. The structural refinement indicates that the as-prepared phosphors crystallize in monoclinic phase (C2/m) and there are two Ca sites and one Ba site in host lattice. The doping ions are determined to occupy Ca sites and the emission of Ce³⁺ and Eu²⁺ ions at different Ca sites were identified and discussed. Since bright blue and yellow emissions were observed from Ce³⁺ and Eu²⁺ ions monodoped CBPO under n-UV excitation, respectively. They were codoped into the CBPO for designing energy transfer from Ce³⁺ to Eu²⁺ to improve the luminescence efficiency of Eu²⁺. In addition, Tb³⁺ ions were added into the CBPO:Ce³⁺ system for realizing highly efficient green emission. The energy transfer mechanisms from Ce³⁺ to Eu²⁺/Tb³⁺ ions were discussed. Interestingly, the incorporation of Mn²⁺ ions into the CBPO:Ce³⁺ system enhanced the blue emission of Ce³⁺ ions due to the modification of crystal lattice. Finally, the thermal stability of CBPO:Ce³⁺, Eu²⁺/Tb³⁺/Mn²⁺ phosphors were investigated systematically and corresponding mechanisms were proposed. Based on these results, the asprepared CBPO:Ce³⁺, Eu²⁺/Tb³⁺/Mn²⁺ phosphors can act as potential blue, yellow, green, and emission-tunable phosphors for n-UV based white LEDs.