Solid-solution red phosphors for white LEDs

Solid solutions of Eu3+-doped metal tungstate and molybdate phosphors were synthesized by solid-state reactions. The crystal structure of the solid-solution phosphors was determined to be tetragonal with a space group of I4(1)/c. The red-emitting solid-solution phosphors exhibited a broad absorption band in the range 220-340 nm and sharp excitation peaks in the near UV to green region. The emission intensities of the solid-solution phosphors were enhanced due to the stiff lattices, as a result of the ordered distribution of cations and anions according to differences in ionic size. The increase in the energy transfer is discussed in terms of metal-ligand distances, ionization potential of Mo and the relatively large overlap between the excitation and emission spectra. Such solid-solution phosphors with a bright red emission intensity, relatively short decay time and appropriate color chromaticity have potential for use as red-emitting materials for white LEDs. (C) 2011 Elsevier B.V. All rights reserved.