Studies On4f^n-15d States And Energy Transfer Of Rare Earth Ions In Na₃Y（BO₃）₂

In recent years, plasma panel display and the scintillator materials have achieved considerable development, but there are some defects with low efficiency of emitting and detecting, stability and lifetime. Researches on new luminescent materials mostly focus on powder materials. Meanwhile, the rapid development of the experimental methods for the synchrotron radiation in VUV range facilitites the investigations on the high-energy excited states of lanthanide ions. The borates have advantages on structure-type, stablility and synthesis. It is more important that the borates can provide various crystal field environments. So the borates become the preferred matrix for luminescent materials doped with rare earth ions. In this paper, new phase Na3Y（BO3）2was selected as the matrix material. The excitation spectra in the VUV-UV region and the emission spectra in UV-Vis range of different trivalent lanthanide ions doped Na3Y（BO3）2were investigated. The lowest energy level position of the4fn-15d states of trivalent lanthanide ions and the energy transfer between two lanthanide ions were discussed.The thesis is divided into following sections:1. Na3Y1-XLnX（BO3）2（Ln=Ce,Pr,Tb,Dy） were prepared by high-temperature solid state reactions. The luminescence properties of single trivalent lanthanide ion doped Na3Y（BO3）2were studied. The lowest energy level position of4fn-15d states were obtained from the corresponding excitation spectra. Comparing the experimental values with those deduced by Dorenbos Model, we believe that the lowest5d states of Ce3+locates at27,472cm-1, and crystal field red-shift factor D（A） is21,868cm-1.2. The excitation spectra of Na3Y0.99Pr0.01（BO3）2and Na3Y0.99Tb0.01（BO3）2show that the lowest4fn-15d energy level positions of Pr3+and Tb3+are40,462cm-1and41,592cm-1, respectively. The experimental values agree well with the values deduced from E（Ce3+） and D（A）. Considering both the D（A） values of Pr3+and Tb3+ions in Na3Y（BO3）2and that of the Ce3+ion, we get D（A） is21,604cm-1.3. The excitation spectra of Na3Y0.99Dy0.01（BO3）2indicate the lowest4fn-15d energy levels position of Dy3+ion is53,475cm-1,which is in accord with the predict value, so the D（A） value is applicable to speculate the lowest positions of4fn-15d states of lanthanide ions in Na3Y（BO3）2. The lowest4fn-15d states of other trivalent lanthanide ions in Na3Y（BO3）2were given. 4. The luminescence properties of Na3Y（BO3）2codped with Ce3+and Tb3+were studied.Tb3+can be sensitizated by Ce3+and the absorbed energies of Ce3+are transferred to Tb3+. Na₃Y（BO3）2: Ce3+,Tb3+takes full advantage of the stong4f-5d transition absorption of Ce3+, the energy transfer between Ce3+-Tb3+convert the ultraviolet light into Tb3+green light effectively.