Synthesis and Luminescent Properties of Na_2Ca_4(PO_4)_2SiO_4∶Eu~(3+),Bi~(3+) Red-emitting Phosphor

Novel red-emit phosphors,Na2Ca4(1-x-y)(PO4)2SiO4∶xEu3+,yBi3+ were synthesized for WLED by conventional solid-state reaction at 1 200 ℃.Effects of the H3BO3 flux,the re-calcination time and doping concentrations of Eu3+,Bi3+ on the luminescence properties were investigated.It was found that a higher Eu3+ emission intensity can be obtained if 30% H3BO3 was added as flux.No apparently structure transformation of the Na2Ca4(PO4)2SiO4 matrix was observed after doping Eu3+,Bi3+.The phosphors give the characteristic emission of Eu3+ at 615 nm under the excitation of 395 nm.Samples re-calcined at 1 200 ℃ for 1.5 h gives a strongest emission.The red emission of Eu3+ can be significantly enhanced by co-doping of Bi3+ via an energy transfer process which involves the charge transfer(CT) transition of Eu3+-O2-→Bi3+→Eu3+.The optimized doping mole fractions of Eu3+ and Bi3+ are x=0.04 and y=0.01,respectively.It shows that the Na2Ca4-(PO4)2SiO4∶Eu3+,Bi3+ is a promising red phosphor for NUV-chips based WLED.