Preparation And Photoluminescence Properties Of Aluminate And Silicate Luminescence Materials Under UV And NUV

Light emitting diodes (LEDs) are the promising new emitting light source for common illumination because of their unique properties in terms of high brightness, high color rendering index, low energy consumption, long lifetime and environment friendliness. So phosphors with ultraviolet (UV), near ultraviolet (NUV) excitation for LEDs, and their fundamental researchs have received much attention. Generally speaking, the phosphors for NUV LEDs must have high absorption efficiency in the NUV and high conversion efficiency into visible light. Additionally, they must have high thermal stability to withstand the high temperature generated by the LED chips. In order to develop such phosphors, rare earth doped aluminate and silicate materials have emerged for their high quantum efficiency and excellent chemical stability. Due to the remarkable development of UV diodes, the combination of an UV chip with red, green and blue phosphors is a valid way to generate white light. Nevertheless, in the three converter system, the blue emission efficiency is low on account of the strong re-absorption of the blue light caused by the red or green emitting phosphors.In order to circumvent this disadvantage, many efforts have been made to realize white light emission in single-phase host by energy transfer between two activators such as Ce3+and Mn2+.Based on the above reasons, we designed and preprared some aluminate and silicate luminescence materials under UV and NUV excitation, and studied their luminescence properties. The main points are listed below:1.SrAl2O4:Eu2+,M1.5Y1.5Al3.5Si1.5O12:Ce3+(M=Mg2+, Ca2+, Sr2+,Ba2+)and LaA103:Eu3+ phosphor were prepared by high temperature solid-state reaction, and their photoluminescence spectra upon NUV excitation were measured. By doping Ba2+/Li+ ions, the emission intensity of SrAl2O4:Eu2+ increased significantly. M1.5Y1.5Al3.5Si1.5O12:Ce3+(M= Mg2+, Ca2+, Sr2+, Ba2+) were effectively excited by blue chip. Upon 450 nm excitation, Mg1.5Y1.5Al3.5Si1.5O12:Ce3+ and Ba1.5 Y1.5Al3.5Si1.5O12:Ce3+ samples show green and yellow emissions, respectively. Under 328 nm excitation, LaA103:Eu3+sample exhibited intense red emission.2. Ba1.1Sr0.7SiO4:0.2Eu2+, NaYSiO4:Eu3+, NaYSiO4:Ce3+, KLaSiO4:Eu3+, KLaSiO4:Ce3+ and KLaSiO4:Ce3+,Mn2+were successful synthesized via high temperature solid-state reaction. The obtained emission spectra of Ba1.1Sr0.7SiO4:0.2Eu2+ indicated that the luminescence intensities of samples have a significant decline by the extension of sintering time. Meanwhile, the luminescent properties of Ba1.1Sro.7-xSiO4:0.2Eu2+, xSb3+(0≤x<0.1) were explored. After introducing the Sb3+ ions into the Ba1.1Sr0.7SiO4:0.2Eu2+, the emission intensity of Ba1.1Sr0.64SiO4:0.2Eu2+ increased significantly due to the energy transfer from Sb3+ ions to Eu2+ ions. Under UV excitation, NaYSiO4:Eu3+/KLaSiO4:Eu3+ and NaYSiO4:Ce3+/KLaSiO4:Ce3+ material exhibited red and blue emissions, respectively. The energy transfer from Ce3+ to Mn2+ in KLaSiO4:Ce3+, Mn2+ phosphor has been validated and demonstrated to be a resonant type via a dipole-quadrupole mechanism by analyzing the relationship of luminescence intensities. By the efficient energy transfer between Ce3+ and Mn2+ in KLaSiO4:Ce3+, Mn2+, the emission color can be tuned from blue to yellow. The composition optimized KLa0.96SiO4:0.02Ce3+,0.02Mn2+ sample exhibited the white light.