Luminescence Enhancement of La4Ti9O24:Eu3+ Red-Emitting Phosphors Via Cation-Substitution of M (ga, Nb, Ta, Zr, Al) Ions

Eu3+- and M (Ga3+, Nb5+, Ta5+, Zr3+, Al3+)-co-doped La4Ti9O24 phosphors were prepared by the solid-state reaction method. The structural phase formation, luminescence properties, and possible LED-lighting application were investigated. The undoped La4Ti9O24 shows an indirect transition with a band-energy of 2.88 eV La4Ti9O24 has a broad intrinsic emission band (350-700 nm) peaked at 530 nm (2.34 eV) at 300K. Eu3+ -doped La4Ti9O24 presents red luminescence from D-5(0)-> F-7(J) (J = 0, 1, 2, 3, 4) transitions, which was obviously enhanced with the cation-substitution of M (Ga3+, Nb5+, Ta5+, Zr3+, Al3+) on Ti4+ sites in the lattices. The typical thermal quenching of La3.72Eu0.28Ti8.55M0.45O24 (M = Al) phosphor is Delta E = 0.342 eV. Importantly, the optical excitation of the samples fit well with the commercial LED-chip because of its efficient absorption in near-UV region (395 nm) and blue (465 nm) wavelength region. The red-LED device packaging with the optimal phosphor was achieved, which has a luminous efficiency of 42 lm/W with a working current of 200 mA and a testing voltage of 3.2 V. The experiments suggest that the phosphor could be potential for solid-state LED-lighting and display.