Single-component and white-emitting garnet-type phosphors Li3Y3Te2O12: Dy3+, Eu3+ with tunable color and high thermostability: Synthesis, luminescence and energy transfer

The discovery of novel Dy3+- activated and Dy3+/Eu3+ co- activated Li3Y3Te2O12 phosphors with garnet-type was successfully achieved by high temperature solid-state sintering method. The phase purity, effects of the doping concentration of sensitizer and activator on the phase structure, as well as morphology characterization were ascertained using X-ray powder diffraction, the Rietveld refinement method, Fourier transform infrared spectrum and scanning electron microscope. Morphology and detailed photoluminescence behavior were examined via chromaticity coordinate of International Commission on illumination, steady-state and dynamic fluorescence spectra. The absorption spectrum of phosphors mentioned above possess strong response in the range of 350–400 nm, and the white-light emission spectrum consisting of two comparable intensities of blue- and yellow-emitting. The yellow one belongs to the hypersensitive forced dipole transition of 4F9/2–6H13/2, originated from inversion asymmetry of Dy3+ occupied sites in Li3Y3Te2O12 matrix. The concentration quenching mechanism of Dy3+ were identified to be the interactions between dipoles. Dy3+ → Eu3+ energy transfer phenomenon in Li3Y3Te2O12 host were observed and evaluated via PL curves and decay process. The Dexter’s theory and Reisfeld’s approximation are employed to reveal the energy transfer mechanism between sensitizers and activators and energy transfer efficiency in depth. The results indicate that utilizing Dy3+ → Eu3+ energy transfer was conducive to promote white → red tunable color emission. Furthermore, the as-prepared phosphors have been proved to own excellent thermal stability, indicating that it can be used as a promising single-component and white-emitting candidate in the design of ultraviolet-pumped white solid-state lighting.