Synthesis and photoluminescence enhancement of Ca3Sr3(VO4)4:Eu3+ red phosphors by co-doping with La3+

In this study, a series of red-emitting Ca3Sr3(VO4)4:Eu3+ phosphors co-doped with La3+ was prepared using the combustion method. The microstructures, morphologies, and photoluminescence properties of the phosphors were investigated. All Ca3Sr3(VO4)4:Eu3+, La3+ samples synthesized at temperatures greater than 700 ℃ exhibited the same standard rhombohedral structure of Ca3Sr3(VO4)4. Furthermore, the Ca3Sr3(VO4)4:Eu3+, La3+ phosphor was effectively excited by near-ultraviolet light of 393 nm and blue light of 464 nm. The strong excitation peak at 464 nm corresponded to the 7F0→5D2 electron transition of Eu3+. The strong emission peak observed at 619 nm corresponded to the 5D0→7F2 electron transition of Eu3+. Co-doping with La3+ significantly improved the emission intensity of Ca3Sr3(VO4)4:Eu3+ red phosphors. The optimum luminescence of the phosphor was observed at Eu3+ and La3+ concentrations of 5% and 6%, respectively. Moreover, co-doping with La3+ also improved the fluorescence lifetime and thermal stability of the Ca3Sr3(VO4)4:Eu3+ phosphor. The CIE chromaticity coordinate of Ca3Sr3(VO4)4:0.05Eu3+, 0.06La3+ was closer to the NTSC standard for red phosphors than those of other commercial phosphors; moreover, it had greater color purity than that of all the samples tested. The red emission intensity of Ca3Sr3(VO4)4:0.05Eu3+, 0.06La3+ at 619 nm was ~1.53 times that of Ca3Sr3(VO4)4:0.05Eu3+ and 2.63 times that of SrS:Eu2+. The introduction of charge compensators could further increase the emission intensity of Ca3Sr3(VO4)4:Eu3+, La3+ red phosphors. The phosphors synthesized herein are promising red-emitting phosphors for applications in white light-emitting diodes under irradiation by blue chips.