Preparation, luminescence properties and energy transfer of Ca 9 Y(PO 4 ) 7 : Eu 2+ ‐Tb 3+ phosphors

Tb 3+ ‐doped and Eu 2+ , Tb 3+ co‐doped Ca 9 Y( PO 4 ) 7 phosphors were synthesized by conventional solid‐state method. Additionally, the luminescence properties, decay behavior and energy transfer mechanism have already been investigated in detail. The green emission intensity of Tb 3+ ions under NUV excitation is weak due to its spin‐forbidden f‐f transition. While Eu 2+ can efficiently absorb NUV light and yield broad blue emission, most of which can be absorbed by Tb 3+ ions. Thus, the emission color can be easily tuned from cyan to green through the energy transfer of Eu 2+ →Tb 3+ in Ca 9 Y( PO 4 ) 7 :Eu 2+ ,Tb 3+ phosphor. In this work, the phenomenon of cross‐relaxation between 5 D 3 and 5 D 4 are also mentioned. The energy transfer is confirmed to be resulted from a quadrupole‐quadrupole mechanism.