Preparation And Properties Of Sr₃SiO₅: Ce³⁺, Li⁺ And LuAG:Ce³⁺ Phosphors For White LEDs

As a new generation of solid-state light source, white LED lighting has many advantages,such as low power consumption, long service life, fast response, high efficiency, small size,safety, etc. The mainstream of white LED is blue chip coupled with yellow phosphor encapsulation, whose main problems are the high color temperature, low color rendering, glare,leading to difficultly application in indoor lighting. However, near ultraviolet LED can effectively solve the above problems, because of high photoelectric conversion efficiency,high efficiency of development, low temperature, high color rendering. In addition, it can effectively solve the problem of glare. Therefore, Green and yellow phosphors for near ultraviolet LED play an important role.In this paper, Sr3SiO5 and Lu AG yellow phosphors were prepared through high temperature solid-state reaction with Ce3+ ions as activator, and Li+ as charge compensation.The phase structure, fluorescence properties and morphology of phosphor were charactered by XRD, PL, TG, DSC, CIE, SEM and so on. The concentration quenching mechanism were discussed. The results show as follow:Sr3SiO5 phosphors were prepared by high temperature solid phase synthesis method. The synthesized phosphors belong to tetragonal crystal system structure, P4/NCC space group structure. The excitation band is in the range of 270~500 nm, peaking at 328 nm and 410 nm.The emission spectrum distribute in 420~650 nm range with the peak located at 528 nm.According to the principle of Dexter, concentration quenching is due to the dipole- dipole interaction of Ce3+. BaF2 flux also has effects on the luminescence properties of the synthesized phosphor, and can improve the growth of crystals, and reduce the reunion phenomenon.Besides, when the Ba2+-doping concentration increases up to 0.4 mol, the emission peak of Sr3-xBaxSiO5: Ce3+, Li+ shows a red-shift from 526 nm to 533 nm; and then when the Ba2+-doping concentration above 0.4 mol, the blue-shift occurs from 533 nm back to 526 nm.The optimal concentration of Ba2+ ion is 0.4mol. With the increase of the Ca2+ doping concentration, the emission peak position has a blue shift from 538 nm to 526 nm, and the strongest excitation intensity is 0.6mol.Ce3+ doped Lu3Al5O12 was synthesized by high temperature solid-state reaction method.The excitation spectrum is in the range of 300~500 nm with two bands peaking at 348 nm and450 nm, respectively. And the emission spectrum locates in 450~650 nm with the peak at 504 nm from transition of 5dâ†'4f(2F7/2, 2F5/2) in Ce3+. According to Dexter’s theory, the concentration quenching effect is attributed to the ion exchange interaction of Ce3+. Compared with LuAG: Ce3+, Sr3SiO5: Ce3+, Li+ phosphors have wider half peak width, illustrating the higher energy conversion efficiency of Sr3SiO5: Ce3+, Li+ phosphors.