Synthesis And Photoluminescence Of Vacuum Ultraviolet Excited Nanoscale And Mircoscale Red Phosphors

In this paper, VUV-excited red nanophosphor has been investigatied. For current research status, two questions about nanophosphor has been evaluated and discussed:improving the luminescence performance of the nanophosphor under VUV excitation and studing the luminescence meachiem. Two common red VUV phosphors, YBO3:Eu3+and YVO4:Eu3+, have been used to study these comtents:morphology controlling, improving photoluminescence (PL) characteristic by doping, and doping mechanism, etc.. And base on these, several novel red phosphors have been discovered. The main conclusions are listed as following:1. From the point of view of improving PL performance, YBO3:Eu3+ nanophosphor has been synthesized by hydrothermal reaction. The PL properties of YBO3:Eu3+ nanophosphors have been adjusted acorrding to change the reaction condition, such as reaction temperature, heat treatment temperature, kind and ratio of organic solvent, kind and amount of surfactants, and so on. The optimal reaction condition is as follow:230℃,3h reaction,900℃,2h heat treatment, using isopropanol and ratio is at 1:1, and using CTAB and the concentration is at 5%(MCTAB=M阳离于=5 %). At last, the optimal nanosample has stonger PL intensity than its bulk counterparts. Its PL intensity reaches to 78.83% of commercial phosphor KX-504A, and the color purity are better.2. Acorrding to compare the different PL characteristic of YBO3:Eu3+ nanophosphor under UV and VUV excitation, the unique PL properties of nanophosphors under VUV excitation has been investigated. And base on these properties, the possible mechanism of VUV excitation are adopted. Different particle size of YBO3:Eu3+nanophosphors have been synthesized by using a simple hydrothermal reaction under different holding times. With change the paticle size of YBO3:Eu3+nanophosphors, the change trends of luminescent intensity under UV and VUV excitation are almost contrary. It is due to small penetration depth of VUV light. And then, series of different concentrations of Eu3+doping in YBO3 nanophosphors were successfully prepared by a modified hydrothermal reaction. In comparison with the change trend of emission intensities in UV spectra, we found a unique phenomenon in the VUV spectra of YBO3:Eu3+nanophosphors: the PL intensities are not sensitive to the activator doping concentrations. We gave a detailed explanation to this phenomenon by using the "self-purification" effect in nanosystems. It will cause effective activator amounts for VUV luminescence to be very low.3. A series of different concentrations of Eu3+doping in YVO4 nanophosphors were prepared by simple hydrothermal reaction. Base on this, co-doping Gd3+ and P5+as sensitizers into YVO4:Eu3+nanophosphors. Although the PL intensity of Gd3+ doped sample increases to some extent, the PL intensity changes with the concentration of Gd3+irregular. Futhermore, the P5+ doped into YVO4:Eu3+ were all harmful to the PL intensities. The change of the PL intensity is more significant with the crystallinity. Combining the self-purification effect of nanoparticles, the relationship was investigated, which between quchening and the amount of lattice sites which could be doped. The quenching concentration of nanophosphor must be related with the amount of doping sites. When all the sites were occupied, two statuses would happen:luminescence quenching and morphology change.4. We design a two step reaction process to prepare the series of Y(V,P)O4:Eu3+ and (Y,Gd)(V,P)O4:Eu3+ nanophosphors. The process include YVO4:Eu3+ seeds synthesis by hydrothermal reaction and co-doping P5+ and Gd3+ in sol-gel process. The morphology and size of the nanophosphors could be controlled by adjusting the molar ratios between seeds and doping ions. Owning to the effect of seeding growth, most of the samples keep spherical-like morphology and narrow size distribution. Comparing with commercial phosphors KX-504A, the composition-optimized (Y,Gd)(V,P)O4:Eu3+ nanophosphors prepared by the two steps reaction with spherical morphology and narrow size distribution, exhibit better red emission and superior color saturation under VUV excitation. The integrated intensity is 71.0% of that for KX-504A.5. Several noval phosphor using borate as host were prepared by solid state and sol-gel reactions. Those include Eu3+/Tb3+ doped CaB2O4 and SrB2O4, Eu3+ doped Mg2B2O5 and MgB4O7, Eu3+/Tb3+ doped SrB6O10. These phosphors all have good PL performance under UV excitation, but only SrB6O10:Eu3+/Tb3+ has good PL performance under VUV excitation. The quehching concentrations of SrB6010:Eu3+ under UV and VUV excitation are all at 30%. And the quehching concentrations of SrB6O10:Tb3+ under VUV excitation is at 25%. The optimal samples of SrB6O10:Eu3+/Tb3+ reach to 42.9% or 41.92% of that of commercial phosphors, respectively. And they have better color purity (SrB6O10:Eu3+) or short shorter decay time (SrB6O10:Tb3+).