Preparation And Photoluminescent Properties Of Eu²⁺-Activated Oxychloride White-Light-Emitting Phosphor

White light emitting diodes(WLEDs) are considered to be the most potential light sources owing to the high efficiency, low power consumption, long lifetime. The commly used method to produce white light is phosphor-converted white LED(pc-WLED). Therefore the exploration of new fluorescent materials has been a hot area of research. In this work, considering the low color rendering and light efficiency of the commercial white light material, we have designed a novel white light fluorescent material via a single–doped activator into a single-phased host. Then the crystal structure and luminescent properties have been studied in detail. The main contents are as follows:A new kind of Eu2+-activated oxychloride white-emitting phosphors, Sr5(PO4)3-x(BO3)xCl:0.04Eu2+ phosphors(0≤x≤0.5) have been synthesized by high-temperature solidstate reactions, and their crystal structure and luminescent properties are investigated by X-ray Rietveld refinement, electron paramagnetic resonance spectroscopy, photoluminescence and lifetime decays measurement. Replacing part of(PO4)3- with(BO3)3- causes in a contraction and distortion of the unit cell of Sr5(PO4)3Cl:0.04Eu2+ host, inducing an additional Eu2+ yellow emission. Under excitation at 365 nm, a tunable emission including white-light are realized via combining an original blue emission [446 nm, Eu(1)] and induced yellow emission [550 nm, Eu(2)], which are originated from Eu2+ centers occupying two nonidentical Sr sites. The increase of yellow/blue intensity ratio, with increasing(BO3)3- content, was attributed to the increased number ratio of Eu(2) to Eu(1) and energy transfer from Eu(1) to Eu(2) sites, as evidenced by spectral overlap and emission decays. More importantly, the phosphors show a higher color rendering index(Ra = 91 and R9 = 90.2) under excitation at 365 nm in comparison with that(Ra = 80, R9 =14.3) of the commercial YAG:Ce3+-based white-light-emitting diode. These results indicate that this single-phased Sr5(PO4)3-x(BO3)xCl:0.04Eu2+ white-light phosphor have a great potential application as a near-UVconverted phosphor for white light-emitting diodes.Furthermore, we studied the influence of the doped cations with different radius on lattice structure and luminescent properties. Eu2+ cells occupy and the behavior of energy transfer between different Eu2+ cells are investigated by X-ray Rietveld refinement, photoluminescence and lifetime decays measurement. The research indicated that the doping of Ca/Ba results in the unit cell volume contraction/expansion and distortion. After the doping of Ca with small radius, Eu tends to form luminous center Eu(1). The energy transfer efficiency between Eu(1) and Eu(2) decreases with the decresing of the number of receptor Eu(2), leading to the enhancement of the blue light emission relative to the yellow emission. After the doping of Ba with large radius, the phenomenon is the opposite. These results confirm that the analysis about stromal cells for Eu2 + is correct.In conclusion, this single-phased Sr5(PO4)3-x(BO3)xCl:0.04Eu2+ white-light phosphor have a great potential application as a near-UV-converted phosphor for white light-emitting diodes. And in this work, the luminescence properties is tuned based on the matrix control, suggesting a certain theoretical and practical significance for the optimization and exploration of white LED with fluorescent material.