Research On Preparation And Luminescent Properties Of Several Oxides With Rare Earth Dopping

Phosphors samples of Ba4(Si3O8)2:Eu2+, R13+(Ri3+=Ho3+, Dy3+, Nd3+), Ba2ZnSi207: Ce3+, Tb3+,Ba2ZnSi207:Eu2+, R23+(R23+=Ho3+,Pi3+,Dy3+) and CaMgP2O7:Ce3+, Tb3+ were synthesized via high temperature solid state reaction. The phase structure of samples was investigated by XRD, the luminescence property was analysed by diffuse reflectance spectra, excitation and emission spectra, fluorescence lifetimes, afterglow decay, and the carriers traps were analysed by thermoluminescence (TL). The main research results are as follows:(1) The long afterglow phosphors Ba4(Si3O8)2:Eu2+,Re3+(Re=Ho, Dy, Nd, Pr, Gd) were obtained by the high-temperature solid state reaction. Only Eu ions act as the luminescent centers in these samples, and no other luminescent center appeared with RE3+ co-doping. There is no obvious influence to the luminescence property of Ba4(Si3O8)2:Eu2+ with Pr3+ or Gd3+ co-doping. The afterglow increases with Dy3+ co-doping lasting for half hour. The fluorescence and afterglow intensities obviously magnify with Nd3+ co-doping, and the afterglow time prolongs for one hour. Ba4(Si3O8)2:Eu2+, Ho3+ shows a long-lasting phosphorescence whose duration is more than 10 h visible to the naked eyes, and the initial phosphorescence intensity is over 3cd/m2. The thermoluminescence analysis shows that the afterglow mechanism of three samples is different. Ba4(Si3O8)2:Eu2+, Dy3+ has deep traps with strong constraint to the carriers, which is disadvantageous to the afterglow property. The concentration of deep traps remains about 50% 10h later, meaning that Ba4(Si3O8)2:Eu2+, Dy3+ is an excellent phosphor material to stock up energy. The process releasing carriers of Ba4(Si3O8)2:Eu2+, Nd3+ is the second order kinetics, and the carriers are captured once again after being released which is important to prolong the afterglow time. The inner traps energy of Ba4(Si3O8)2:Eu,Ho3+is a energy band ranging from 0.608eV to 1.156eV with advantageous traps depth and large carriers concentration, deciding that Ba4(Si3O8)2:Eu2+,Ho3+ is an excellent afterglow materal.(2) Afterglow phosphors Ba2ZnSi2O7:Eu2+ and Ba2ZnSi207:Eu2+,RE3+ (RE:Ho, Pr, Dy) are synthesized by a solid state reaction. All samples show broad emission bands of Eu2+ centered at 505 nm. The fluorescence intensity is depressed obviously with Ho3+, Pr3+ or Dy3+ co-doping. Ba2ZnSi2O7:Eu2+ exhibited long-lasting phosphorescence for 15 minutes or so. Afterglow duration is 1 hour with Ho3+ co-doping and 2 minutes with Dy3+ co-doping. There is no obvious influence on the afterglow property with Pr3+ co-doping. According to the analysis of TL curves of samples, the traps depth is too deep (1.252eV) to release the trapped carriers with Dy3+ co-doping, bringing on the poor afterglow. There are suitable traps depth (0.854eV) and high concentration of trapped carriers with Ho3+ co-doping, resulting in longer afterglow duration(3) Ce3+ or Tb3+ doped and Ce3+/Tb3+ co-doped Ba2ZnSi2O7 phosphors were prepared via the conventional high temperature solid state reaction method. The photoluminescence and energy transfer properties of samples were studied in detail. Ba1.98-xZnSi2O7:0.02Ce3+,xTb3+ shows both a blue emission (428 nm) from Ce3+ and a yellowish-green emission (542 nm) from Tb3+ with considerable intensity under ultraviolet (UV) excitation (352 nm). The emission chromaticity coordinates can be adjusted from blue to green region by tuning the concentration of Tb3+ ions through an energy transfer process. The energy transfer mechanism from Ce3+ to Tb3+ ions was proved to be dipole-dipole interaction. The Ce3+ and Tb3+ co-doped Ba2ZnSi2O7 phosphors are potential UV-convertible candidates with green light emitting in UV-LEDs.