Structure and luminescent properties of new Dy³⁺/Eu³⁺/Sm³⁺-activated InNbTiO₆ phosphors for white UV-LEDs

A series of novel Dy³⁺/Eu³⁺/Sm³⁺-activated InNbTiO₆ phosphors have been prepared by conventional solid state reaction method. Based on the structure refinement, RE³⁺ ions are preferred to occupy the site of In³⁺ (2e) in the wolframite-type host lattice. According to their UV–visible diffusion reflectance spectra, the band gap and absorption property of un-doped InNbTiO₆ sample can be tuned by the dopants. Under UV–visible light excitation, Dy³⁺/Eu³⁺/Sm³⁺ activators in this matrix mainly show emission lines originating from their characteristic f→f transitions. The optimal excitation and emission wavelength are 385 nm and 581 nm for Dy³⁺, 394 nm and 616 nm for Eu³⁺, 406 nm and 615 nm for Sm³⁺. Concentration quenching occurs at 0.06 for Dy³⁺, 0.06 for Eu³⁺, and 0.04 for Sm³⁺, ascribed to resonant q-q, q-q, and d-q interactions, respectively. The luminescence lifetimes are determined to be 0.13, 0.50, and 0.50 ms for InNbTiO₆:0.06Dy³⁺, InNbTiO₆:0.06Eu³⁺, and InNbTiO₆:0.04Sm³⁺, respectively. The Dy³⁺, Eu³⁺, and Sm³⁺ doped phosphors exhibited yellowish-white, red, and orange-red luminescence, respectively. The quantum yields and thermal stability of representative phosphors have been investigated. Present work shows that these new phosphors are promising for application in UV-LED solid-state lighting devices.