Microstructure And Luminescent Properties Of The Rare Earth-doped Borate Phosphors And Glasses

Borate material is an excellent functional material with multiplicate chemical structure, good thermal stability, wide band gap and low manufacturing cost. In recent years, it became attractive in optical glass and phosphors applications. The structure modification on the host lattice by introducing hetero-cations may improve effectively the luminescence intensity of a phosphor. In this paper, different cation doped BaZr(BO₃)₂:Eu phosphor and Eu³⁺, Er³⁺, Pr³⁺-doped BaO-(x/2)Al₂O₃-(1-x)SiO2-B2O3 glass are synthesized and the crystal field effect on the electronic transition of rare earth ions were studied.BaZr(BO₃)₂:Eu phosphors are prepared by conventional solid-state reaction. The effects of structural change by Al³⁺,Si4+ doping on luminescence of Eu³⁺ ions are discussed. The slight shrink of crystal cell after co-doping can be due to the smaller radius Al³⁺,Si4+ ions. The absorption intensity of BaZr(BO₃)₂:Eu phosphors exhibit increased trend through doping, and the excitation peaks show blue shift. The intensity parameters are calculated from emission spectra by Judd-Ofelt theory. The results display great affect on the symmetry of Eu³⁺ ion by cations doping. The site symmetry around Eu³⁺ is tuned after doping and results in the change of transition probabilities. The quantum efficiencies of cations doped samples are improved and validated by Judd-Ofelt calculation.Er³⁺ or Pr³⁺ doped Al₂O₃-(1-x) SiO2-B2O3 glasses are synthesized by solid-state reaction. The intensity parameters of Er³⁺ or Pr³⁺ doped Al₂O₃-(1-x) SiO2-B2O3 glasses are calculated by Judd-Ofelt theory. The calculatedΩ2 increases with increased amount of SiO2. This means that Er ions are under disorder or non-symmetry local environments with Si doped. The upconversion luminescence at 541nm (⁴S_3/2—⁴I_15/2), 659nm (4F9/2—4I15/2) combined with 1550nm (4I13/2—4I15/2) transitions of Er³⁺ samples are obtained under 980nm LD excitation. The emission of Pr³⁺-doped glasses belong to ¹G₄—³H₅ (1300nm) , 3P0—3F4 (718 nm),3P0—3F2 (635 nm),3P0—3H6 (608 nm),³P₁—³H₄ (482nm) transitions are observed. The calculated transition oscillator strength and integrated emission cross section show that it is promising laser and optical amplified materials.Phonon energy of BaO-Al₂O₃-B₂O₃ and BaO-SiO₂-B₂O₃ glasses are discussed by Eu³⁺ as probe. Compared to BaO-Al₂O₃-B₂O₃ glass, Eu³⁺ ions are in more non-symmetry crystal environment for BaO-SiO₂-B₂O₃ glass. The non-radiative transition probability is calculated through multi-phonon relaxation theory and Judd-Ofelt calculation also confirmed the result, respectively. The electric dipole energy transfer rates between Eu³⁺ can be ignored at low concentration doping accroding to calculated results.