Preparation and photoluminescence properties of Eu 3+ ion-doped Mg 2 LaTaO 6 phosphor

The luminescent properties of Eu3+ ion-doped Mg2LaTaO4 phosphors were synthesized using a vibrating milled solid-state reaction. The XRD results show that the crystal structure of the Mg2LaTaO4:Eu3+ phosphor that is calcined at 1450 °C for 8 h has a cubic structure and the (440) diffraction peak shifts to a higher diffraction angle when the Eu3+ ion concentration increases. The absorption spectra results show that the absorption band d in the range 190–400 nm is attributed to absorption of pure Mg2LaTaO4 by the host lattice. When Mg2LaTaO4 is doped with Eu3+ ions, the broad band that is centered at 295 nm is assigned to the charge transition state (CTS) for the interaction of O2− and Eu3+ with the Mg2LaTaO4 host lattice. The sharp peaks from 310 to 550 nm are attributed to the typical intra-4f transitions of Eu3+ ions. When the phosphor is excited using either 393 or 464 nm there is a red emission at 605 nm that is attributed to the electric dipole transition (5D0 → 7F2) for the Eu3+ ion. The asymmetry ratio is about 2–2.5, which lies well within the range of usual values for oxide glasses, which demonstrates that the Eu3+ ions occupy low-symmetry sites. The maximum intensity of the photoluminescence for the 5D0 → 7F2 transition occurs at an Eu3+ ion concentration of 30 mol%, which demonstrates that there is concentration quenching at higher Eu3+ concentrations. The critical distance is about 7.68 A for the 5D0 (J = 3, 2, 1) transition and the energy transfer is characterized as a wave-function exchange.