Luminescence enhancement of La4Ti9O24:Eu3+ red-emitting phosphors via cation-substitution of M (Ga, Nb, Ta, Zr, Al) ions

Highlights: • Cation-substitution of (Ga³⁺, Nb⁵⁺, Ta⁵⁺, Zr³⁺, Al³⁺) on Ti⁴⁺ significantly improve luminescence of La₄Ti₉O₂₄:Eu³⁺. • The phosphor can be efficiently excited by near-UV and blue light and emitted pure red light. • The red luminescence of the phosphors presents high thermal stability. • Excellent luminous performance was obtained in the fabricated LED devices. 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 2.88eV La₄Ti₉O₂₄ has a broad intrinsic emission band (350–700nm) peaked at 530nm (2.34eV) at 300K. Eu³⁺-doped La₄Ti₉O₂₄ presents red luminescence from ⁵D₀→⁷F_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 La_3.72Eu_0.28Ti_8.55M_0.45O₂₄ (M=Al) phosphor is ΔE=0.342eV. Importantly, the optical excitation of the samples fit well with the commercial LED-chip because of its efficient absorption in near-UV region (395nm) and blue (465nm) 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 200mA and a testing voltage of 3.2V. The experiments suggest that the phosphor could be potential for solid-state LED-lighting and display.