Energy transfer mechanism and color controllable luminescence in Dy3+/Eu3+-codoped NaLa(MoO4)2 phosphors

Abstract

Dy3+/Eu3+-codoped as well as Dy3+-doped NaLa(MoO4)2 phosphors were synthesized via a facile solid-state reaction method. The X-ray diffraction patterns, field-emission scanning electron microscope images, photoluminescence (PL) spectra and decay curves were employed to characterize the synthesized samples. Under the excitation of 387 nm, all the Dy3+-doped NaLa(MoO4)2 phosphors exhibited the characteristic emissions of Dy3+ ions (blue emission at 486 nm: 4F9/2 → 6H15/2 and yellow emission at 573 nm: 4F9/2 → 6H13/2). Furthermore, the PL emission intensity increased with Dy3+ ion concentration and the concentration quenching effect occurred when the Dy3+ ion concentration was over 5 mol%. Meanwhile, color-tunable emissions were observed in Dy3+/Eu3+-codoped NaLa(MoO4)2 phosphors owing to the efficient energy transfer (ET) from Dy3+ to Eu3+ ions. Through theoretical calculation, it was evident that the ET efficiency increased gradually with the increment of Eu3+ ion concentration, reaching ∼ 70% of its maximum value at 9 mol% of Eu3+ ion concentration. Additionally, the ET mechanism between Dy3+ and Eu3+ ions was found to be electric dipole–dipole interaction.