Optical properties and energy transfer of NaCaPO4: Tb3,Eu3+ phosphors

A novel yellow-emitting phosphor NaCaPO4:Tb3+,Eu3+ was synthesized using a conventional, solid-state reaction for solid-state lighting applications. The luminescence properties supported the occurrence of energy transfer from Tb3+ to Eu3+ ions. The energy transfer mechanism was studied and demonstrated to be a quadrupole–quadrupole interaction. The decay curves of NaCaPO4:0.04Tb3+,xEu3+ phosphors further confirmed the existence of energy transfer from Tb3+ to Eu3+ ions. This energy transfer induced a change in the emitted color of the phosphors from green to yellow, which can be obtained by appropriately tuning the Eu3+ concentration. The results indicated that NaCaPO4:Tb3+,Eu3+ provided a clue for the search of phosphors for white-light-emitting diodes.