EFFECT OF Eu3+ ION DOPING CONCENTRATION ON THE STRUCTURE AND OPTICAL PROPERTIES OF LSTO FLUORESCENT POWDERS PREPARED BY SOLID-STATE REACTION METHOD

Abstract

LSTO fluorescent powder doped with Eu³⁺ ions with 1 to 6% concentrations by solid-state reaction method at 1200 ^oC. The obtained material is a multiphase structure with main phases La₂SrTiO₆, SrTiO₃ and La₂O₃, with an average size from 3 to 4 µm, with the structure almost independent of Eu doping concentration. The obtained material strongly absorbs in the ultraviolet and visible regions with characteristic absorption peaks of LSTO substrate material with CTB band at 288 nm and fluorescence excitation peaks of Eu³⁺ ions at positions 361, 375, 384, 395, 402, 414, 465, 474, 526 and 536 nm. The material gives the best emission when excited at 395 nm, corresponding to the energy level transition of Eu³⁺ ion from the ground state ⁷F₀ to the state ⁵L₆. When excited at 395 nm, the fluorescent powder emits strongly in the red-orange region, with an emission band from 575 to 725 nm, this emission band is the state transition of Eu³⁺ ion from ⁵D₀ to ⁷F_j (j = 0, 1, 2, 3, 4). The phenomenon of fluorescence quenching due to the concentration of the material system is observed at 5% Eu. The obtained fluorescent powder has potential applications in improving the quality of WLEDs when using nUV-LED chips with an emission wavelength of 395 nm.