PL Properties of Sr2CeO4 With Eu(3+) and Dy(3+) for Solid State Lighting Prepared by Precipitation Method

Photoluminescence studies of pure and Dy(3+), Eu(3+) doped Sr2CeO4 compounds are presented by oxalate precipitation method for solid state lighting. The prepared samples also characterized by XRD, SEM (EDS) and FTIR spectroscopy. The pure Sr2CeO4 compound displays a broad band in its emission spectrum when excited with 280 nm wavelength, which peaks centered at 488 nm, which is due to the energy transfer between the molecular orbital of the ligand and charge transfer state of the Ce(4+) ions. Emission spectra of Sr2CeO4 with different concentration of Dy(3+) ions under near UV radiation excitation, shows that intensity of luminescence spectra is found to be affected by Dy(3+) ions, and it increases with adding some percentages of Dy(3+) ions. The maximum doping concentration for quenching is found to be Dy(3+) = 0.2 mol % to Sr(2+)ions. The observed broad spectrum from 400 to 560 nm is mainly due to CT transitions in Sr2CeO4 matrix and some fractional contribution of transitions between (4)F9/2 → (6)H15/2 of Dy(3+) ions. Secondly the effect of Eu(3+) doping at the Sr(2+) site in Sr2CeO4, have been studied. The results obtained by doping Eu(3+) concentrations (0.2 mol% to 1.5 mol%), the observed excitation and emission spectra reveal excellent energy transfer between Ce(4+) and Eu(3+). The phenomena of concentration quenching are explained on the basis of electron phonon coupling and multipolar interaction. This energy transfer generates white light with a color tuning from blue to red, the tuning being dependent on the Eu(3+) concentration. The results establish that the compound Sr2CeO4 with Eu(3+) = 1 mol% is an efficient "single host lattice" for the generation of white lights under near UV-LED and blue LED irradiation. The commission internationale de I'Eclairage (CIE) coordinates were calculated by Spectrophotometric method using the spectral energy distribution of prepared phosphors.