Effect of Gd/La substitution on the phase structures and luminescence properties of (La,Gd)Sr2AlO5:Ce3+ solid solution phosphors
A series of yellow-emitting La0.975−xGdxSr2AlO5:0.025Ce3+ phosphors have been synthesized by a solid-state reaction. All the samples retain the same tetragonal crystal structure, and the phosphors emit yellow emission with a peak maximum shifting from 540 nm to 556 nm, depending on the Gd/La ratio, when excited by 440 nm blue light. Their temperature dependent photoluminescence, fluorescence decay curves, and CIE values were also discussed. With increasing Gd/La ratio, the red-shift behaviors can be ascribed to the enhancing covalence, and the emission intensities first increased, then decreased, and finally increased to the maximum at x = 0.6. A white light-emitting diode (w-LED) lamp was fabricated based on the selected yellow-emitting La0.375Gd0.6Sr2AlO5:0.025Ce3+ phosphors combined with a 460 nm blue-emitting InGaN chip. The packaged w-LED lamp gave CIE chromaticity coordinates of (0.3562, 0.3660) with a warm color temperature of 4664 K and a color rendering index of 83.