Photoluminescence properties of LiTi2 - x Eux (PO4 )3 phosphor.

A solid-state reaction route-based LiTi2 - x Eux (PO4 )3 was phosphor synthesized for the first time to evaluate its luminescence performance by excitation, emission and lifetime (τ) measurements. The LiTi2 - x Eux (PO4 )3 phosphor was excited at λexci. = 397 nm to give an intense orange-red (597 nm) emission attributed to the 5 D0 → 7 F1 magnetic dipole (ΔJ = ±1) transition and red (616 nm) emission (5 D0 → 7 F2 ), which is an electric dipole (ΔJ = ±2) transition of the Eu3+ ion. Beside this, excitation and emission spectra of host LiTi2 (PO4 )3 powder were also reported. The effect of Eu3+ concentration on luminescence characteristics was explained from emission and lifetime profiles. Concentration quenching in the LiTi2 - x Eux (PO4 )3 phosphor was studied from the Dexter's model. Dipole-quadrupole interaction is found to be responsible for energy transfer among Eu3+ ions in the host lattice. The LiTi2 - x Eux (PO4 )3 phosphor displayed a reddish-orange colour realized from a CIE chromaticity diagram. We therefore suggest that this new phosphor could be used as an optical material of technological importance in the field of display devices. Copyright © 2016 John Wiley & Sons, Ltd.

Energy transfer based emission analysis of (Tb³âº, Sm³âº): lithium zinc phosphate glasses.

The present paper reports on the results pertaining to photoluminescence properties of Tb(3+), Sm(3+) and energy transfer from Tb(3+) to Sm(3+) ions in lithium zinc phosphate (LZP) glass matrix prepared by melt quenching method. Besides photoluminescence studies thermal stability for the LZP glass is also evaluated from TG-DTA measurement. Tb(3+) doped glasses have exhibited a prominent green emission at 547 nm assigned to (5)D4→(7)F5 transitions on exciting at λ(exci)=377 nm. The quenching phenomenon in Tb(3+) emission on varying its concentration has been discussed from cross-relaxations. Sm(3+) incorporated glasses have shown strong orange emission at 603 nm assigned to (4)G5/2→(6)H7/2 transition upon exciting with λ(exci)=404 nm. The possibility of energy transfer process taking place between these two ions is understood from the significant spectral overlap of Sm(3+) absorption and Tb(3+) emission. Migration of excitation energy from Tb(3+) ions to Sm(3+) ions at λ(exci)=375 nm is evaluated from the emission spectra of (0.5 mol.% Tb(3+)+(0.5-2.0 mol.%) Sm(3+)) co-doped glasses. The emission intensity of Sm(3+) has enhanced while Tb(3+) emission intensity decreased with an increase in Sm(3+) concentration suggesting the occurrence of energy transfer through cross-relaxations from Tb(3+) ((5)D4) to Sm(3+) ((4)G5/2). The mechanism behind energy transfer process has been further explained from energy level diagram, decay profiles and confirmed by calculating energy transfer parameters (energy transfer efficiency (η) and energy transfer probability (P)) of co-doped glasses. The dipole-dipole interaction is found to be more responsible for energy transfer Tb(3+) ((5)D4) to Sm(3+) ((4)G5/2) ions in LZP glass matrix.