Research On Preparation And Luminescent Of Rare Earth Ions Doping Calcium Carbonate

Calcium carbonate is an excellent candidate for phosphor matrix. For there are three crystalline polymorphs of calcium carbonate:calcite, vaterite and aragonite. Different crystal types lead to different luminescent properties. On the other hand, calcium carbonate is a very important chemical material for its advantages of low cost, good chemical stability and physical properties and it has been extensively used in the areas of plastics, paper, paint and building. All these applications provide a wide space for the rare earth luminescent materials based on calcium carbonate.In this dissertation, CaCO3, B2O3, CaCl2, Eu2O3, Bi2O3, CeO2, Li2CO3and Mn(CH2COO)2-4H2O were chosen as the main raw materials to obtain rare earth ions doped or other ions doped CaCO3, CaO or CaCO3-B2O3-CaCl2(CBC) luminescence materials by using the solid state method and combustion method. The crystalline struture, morphology, luminescence properties and afterglow time of phosphors have been investigated by X-ray diffraction(XRD), Scanning Electron Microscope(SEM), fluorescence spectrophotometer and afterglow decay curve.(1) CaCO3:Eu3+, Bi3+and CaCO3:Mn2+phosphors were synthesized by the conventional solid-state reaction method at900℃and650℃, respectively. The results show that the photoluminescence of Eu3+and Bi3+ions co-doped CaCO3samples can be efficiently excited by290nm light. The intense photolummescence near-UV and red are corresponding to the1S0-3P1transition of Bi3+and the5D0-7FJ(J=0,1,2) transition of Eu3+in turn. Moreover, optimal doping concentration is1%(mol) with Eu3+: Bi3+=1:1. As for Mn2+ions doped CaCO3samples, the PL spectra show an intense red light emission (wavelength at610nm), which is corresponding to4T1(4G)-6A1(6S) transition of Mn2+. The optimal doping concentration is0.75%(mol).(2) CaO:Eu3+, Ce3+samples have been synthesized by the traditional solid-state reaction method under reductive atmosphere and the luminescence characteristics were also studied. Energy transfer occurred in Ce3+/Eu3+co-doped CaO due to the partial overlap between the emission spectrum of CaO:Ce3+and the excitation spectrum of CaO:Eu3+. Meanwhile, the luminescence characteristics of Ce3+/Eu3+co-doped CaO was observed. The emission intensity of matrix and Ce3+ions compared with the single-doped Ce3+ions were decreased when the ions concentration of the co-doping Ce3+and Eu3+were1%(mol). Compared to the single-doped Eu3+ions, the primary emission of these codoped samples transform from the magnetic dipole transition(594nm,5D0-7F1) into the electric dipole transition (618nm,5D0-7F2). The overall luminescence intensity increased significantly, which effectively proved the energy transfer of red-emitting phosphor CaO:Ce3+, Eu3+.(3) The phosphor of CBC:Eu2+have been synthesized by the solid-state reaction method under the weak reductive atmosphere at900℃. The emission spectra of phosphor show a yellow-colored broad emission peak at560nm attributed to Eu2+ions transition from4f65d1â†'4f7, which can be excited efficiently in390nm. Other phosphor of CBC:Eu has been synthesized by combustion method at600℃. The emission spectra of phosphor show blue-colored broad emission peak at454nm attributed to Eu2+ions transition from4f65d1â†'4f7and weak red-colored emission, which can be excited efficiently in380nm.(4) Long persistent phosphors of CBC:Eu, Bi with red light emission have been synthesized by high temperature solid-state reaction under the weak reductive atmosphere. The long persistent phosphor emits intense red long-lasting phosphorescence for a longer time after irradiation by UV light. By the luminescence spectra analysis, the long persistent phosphor emission spectra show a red-colored broad emission peak at631nm attributed to Eu2+ions transition from4f65d1â†'4f7when excited in284 nm and463nm. There are also some red-colored sharp peaks which are contributed to Eu3+ions transition from5D0-7FJ(J=1,2,3,4).