Preparation And Photoluminescent Properties Of Phosphors For Mercury-free Fluorescent Lamp

Mercury-free fluorescent lamp has been a research focus in lighting and display fields due to its characteristics of environment protection, quickly starting, and so on. Y2O3:Eu3+phosphor has been widely applied because of its excellent properties. But its cost is high because there is a mout of high price rare earth elements in it. So how to reduce the cost of vacuum ultra-violet (VUV) red phosphor Y2O3:Eu3+is an urgent problem to be solved. VUV blue phosphor BaMgAl10O17:Eu2+Mn2+has better color saturation than BaMgAl10O17:Eu2+phosphor, but the degradation mechanism of this phosphor has not been clearly clarified. Additionally, it is an important study field for mercury-free fluorescent lamp to research and develop new VUV phosphors. In this dissertation, the following aspects are chosen as researching objects: reducing the production cost of commercial red phosphor Y2O3:Eu3+, the degradation mechanism of BaMgAl10O17:Eu2+, Mn2+blue phosphor, and the development of new K3Gd(PO4)2based phosphors. Ca2+co-doping and Y2O3:Eu3+coated Y2O3phosphor are selected to reduce the production cost of Y2O3:Eu3+phosphor. The degradation mechanism of BaMgAl10O17:Eu2+, Mn2+under thermal treatment, UV radation and VUV radation is studied. The new K3Gd0.2(PO4)2:0.8Tb3+VUV green phosphor with high luminance is developed. The main results are listed below:1. The Ca2+co-doped Y2O3:Eu3+phosphors are prepared by solution combustion method. The optimized amout of urea, temperature of thermal treatment, and the concentration of Ca2+are100%of theoretical amount,1400°C, and6mol%, respectively. Under254nm excitation, the intensity of Y1.94-xCaxEu0.06O3increases with the concentration of Ca2+, which is caused by the strengthening of adsorption of254nm by co-doping of Ca2+. Under147nm excitation, the intensity of Y1.94-xCaxEu0.06O3also increases with the concentration of Ca2+2、The Y2O3:Eu3+coated Y2O3particles are prepared by urea assisted homogeneous precipitation. The optimized concentration of (Y, Eu)(NO3)3and reacting time are0.02mol/L and3hours respectively. Under254mm excitation, the intensity of Y2O3:Eu3+coated Y2O3particles equals86%of the intensity of Y2O3sampie prepared under same condition. Under147mm excitation, the intensity of Y2O3:Eu3+coated Y2O3particles equals88%of the intensity of Y2O3sample prepared under same condition. 3.The emission and excitation spectra under UV and VUV excitation, the stability of Eu3+and Mn2+. adsorption spectra and thermoluminesccnce of BaMgAl10O17:Eu2+,Mn2+before and alter thermal treatment, UV radiation and VUV radiation are investigated comparatively. The results indicate that the oxidation and migration of Eu2+are primarily responsible for the thermal degradation of BAM:Eu2+,Mn2+. The UV radiation degradation of samples are primarily involved in the metaslable state of Eu2+The migration of Eu2+resulted in VUV radiation degradation. The serious VUV luminous loss of samples after UV radiation can be partly linked to the interruption of energy transfer from host to activator by traps. The Mn2+in BAM:Eu2+,Mn2+did not alter during the thermal, UV and VUV radiation treatments and is not related to the degradations.4.The K3Gd1-x(PO4)2:Eux3+(0≤x≤1) and K3Gd1-y(PO4)2:Tby3+(0≤y≤1) are prepared by solid stale reaction. The obtained UV excitation and emission spectra indicate that the excitation energy can not be migrated among the activator ions in the K3Gd(PO4)2matrix because of a relatively large distance between the nearest Gd3+neighbors. The strongest emission intensity under147nm excitation is obtained when Eu or Tb concentration is0.8mol. The concentration quenching is affected mainly by the K3Gd(PO4)2host and the number of excited electrons of P-O tetrahedrons. Under147nm excitation, the integrate emission intensity of K3Gd0.2(PO4)2:0.8Tb3+is about204%of commercial phosphor Zn1.96SiO4:0.04Mn2+the chromaticity coordinates of K3Gd0.2(PO4)2:0.8Tb3+is around (0.340,0.561), the decay time of K3Gd0.2(PO4)2:0.8Tb3+is about5.09ms. K3Gd0.2(PO4)2:0.8Tb3+is a potential VUV green phosphor for the mercury-free fluorescent lamps.