Preparation And Luminescent Properties Of Eu³⁺-Sr²⁺ Co-doped Nano-silica Materials

Because of the special electron shell structure, the rare earth- doped luminescence materials has been provide with outstanding luminescence properties than the other type luminescence materials.The abundant and cheap Eu³⁺ was selected as the activated dose of nano-silica material, and the materials were luminous. In the process of preparation of Eu³⁺ doped nano-silica, a definite amount of Sr²⁺ was added . The results showed that Eu³⁺-Sr²⁺ co-doped nano-silica were not only improved the luminescence properties of raw materials, and also produced new luminescence centers. It was very useful to making cheaper and more practical luminescent materials.In this paper with TEOS as precursor, ethanol as solvent, nothing doped , rare earth Eu³⁺ single-doped, Sr²⁺ single-doped and Eu³⁺-Sr²⁺ co-doped nano-silica luminescence materials were prepared by sol - gel method. Using XRD, SEM, DSC-TG, FTIR, PL, and other modern test technology on Eu³⁺-Sr²⁺ doped nano-silica luminescence materials, we characterized and analyzed the structure, phase, morphology, luminescence properties of materials. The affecting factors on the luminescence properties were studied, and its luminescence mechanism were also analyzed.In the pre-stage of preparation the Eu³⁺-Sr²⁺ co-doped nano-silica luminescence materials, the main factors affecting gelation time were analyzed by orthogonal test ,they were alcohol- silicon ratio, silicon-water ratio, aging temperature, reaction time and pH . The results showed that the aging temperature and alcohol-silicon ratio were the important factor affecting the gelation time . Discuss the conditions ,when alcohol-silicon ratio=6:1, silicon-water ratio = 6:1 ,aging temperature=50℃, pH =2, the reaction time is 8 hours, the gelation time is reasonable. The XRD and SEM results showed that Eu³⁺-Sr²⁺ co-doped nano-silica luminescence materials was amorphous.Its particle were very uniform, but has a small amount of agglomeration phenomenon.When the nothing doped of nano-silica materials was irradiated by different wavelength light , the sample can emit ultraviolet radiation band with two peak at 345nm, 360nm and one visible light at 670nm.These emission may be related to oxygen vacancy defects, non-bridging oxygen center defects formed in the material preparation processes .The luminescence properties of Eu³⁺ single-doped silicon was studied. In the emission spectra exist five emission peaks are located at 365nm ,580-590nm, 616nm, 660nm, 710nm. 365nm emission peak where the intensity of the largest is not visible; in the visible spectral range of 616nm was greatest strength, its color is red, is the characteristic spectrum of Eu³⁺. In the visible region 580-590nm, 616nm, 660nm, 710nm emission peak of Eu³⁺ doped silica luminescence materials, were induced by the 5D0-7FJ (J = 0,1,2,3,4) of Eu³⁺ energy transition . The influence of Eu³⁺ ions doped concentration to the luminescence properties was studied . With the Eu³⁺ ion doping concentration increased , the intensity of emission first increased and then decreased; when the doping concentration of 0.5%, the intensity of emission was strongest .The luminescence properties of Sr²⁺ single-doped silicon was studied. In the emission spectra exist two emission peaks appeared at 343nm and 670-690nm . The similar spectrum can be found when compared its excitation and emission spectra with undoped nano-silica material .The addition of Sr²⁺ did not change the luminescence peak position , only made emission peak intense.It played the role only to strengthen .In the emission spectra of the Eu³⁺-Sr²⁺ co-doped silicon luminescent materials there were four main emission peaks.They are located at 409nm, 470nm ,580-590nm, 616nm. It was found that not only the addition of Sr²⁺ ions on the luminescent properties have significant influence, but also the different amount added to their have different effects.And compared it with Eu³⁺ ion doped nano-silica luminescent materials, when Sr²⁺ doping concentration of≤0.5%,the emission peak is almost not changed, but there are different levels of luminous intensity increased; when 0.5% 2+ doping concentration≤1.0%, there appeared 409nm emission peaks which is the department characteristic Eu²⁺ emission peaks. The phenomenon indicating that Sr2 + doped the material converted part of the Eu³⁺ ions into Eu²⁺. The influence of different temperature on the luminescence properties was studied. With the temperature changed, the emission peak position has not changed, but the intensity has changed. The intensity of 409nm emission peak weakened, but 616nm has enhanced in emission intensity.