Photoluminescence enhancement of Ca3Sr3(VO4)4:Eu3+,Al3+ red-emitting phosphors by charge compensation

In this study, Ca3Sr3(VO4)(4):0.05Eu(3+), Ca3Sr3(VO4)(4):0.05Eu(3+),xAl(3+), and Ca3Sr3(VO4)(4):0.05Eu(3+),0.06Al(3+), yM(+) (M = Li, Na, and K) red-emitting phosphors were synthesized by a citric acid-assisted sol combustion method. For the photoluminescence properties and crystal structure characterization of the prepared powder samples, the X-ray diffraction (XRD), photoluminescence (PL) spectroscopy and scanning electron microscopy (SEM) were used. The powder XRD analysis illustrated that the low content of doped Al3+ ions and charge compensators did not have a significant effect on the crystal structure of the prepared samples, and the samples still retained the rhombohedral crystal structure. The SEM images indicated that the charge compensator-doped samples were well crystallized, with a homogeneous particle size distribution. The PL studies revealed that the luminescence intensity was significantly improved by doping Al3+ into Ca3Sr3(VO4)(4):Eu3+. The emission intensity of Ca3Sr3(VO4)(4):0.05Eu(3+),0.06Al(3+) was nearly doubled upon co-doping with the charge compensator M+ (M = Li, Na, and K); the optimal concentration of the charge compensator was 12%. In particular, the maximum emission intensity and particle size were observed when Li+ was co-doped. In addition, the emission intensity of Ca3Sr3(VO4)(4):0.05Eu(3+),0.06Al(3+),0.12Li(+) is about 2.08 times higher than that of Ca3Sr3(VO4)(4):0.05Eu(3+),0.06Al(3+). Its color purity is as high as 95% and the external quantum efficiency is 57.77%. The Ca3Sr3(VO4)(4):Eu3+,Al3+,Li+ system provides potential red phosphors for near-ultraviolet excitation applied in white light-emitting diodes (LEDs).