White Luminescence of Dy3+ Ions Doped 12CaO•7Al2O3 Nanopowders Under UV Light Excitation

12CaO center dot 7Al(2)o(3):Dy3+ nanopowders were successfully synthesized by the chemical co-precipitation method. X-ray diffraction result shows that the single 12CaO center dot 7Al(2)O(3) phase is formed with Dy3+ ions to replace the Ca2+ ions in the host of 12CaO center dot 7Al(2)O(3). The yellow and blue emissions, attributed to the forced electric dipole transition of F-4(9/2) -> H-6(13/2) centered at 571 nm and the magnetic dipole transition of F-4(9/2) -> H-6(15/2) centered at 480 nm, respectively, were observed. The integrated intensity ratios of yellow to blue increase from 1.63 to 1.70 with Dy3+ concentration increasing from 0.8 to 2.0% for the as-prepared 12CaO center dot 7Al(2)O(3):xDy(3+) phosphor. The significantly enhanced emission intensities of 12CaO center dot 7Al(2)O(3):1.0% Dy3+ phosphor annealed at 900 degrees C for 2 hours in vacuum ambient could be ascribed to the decrease of OH- groups and the change of the surface topography. The thermal stability and the Commission International de l'Eclairage coordinates were also investigated. All the photoluminescence characteristics indicate that Dy3+ ions doped 12CaO center dot 7Al(2)O(3) may be a good candidate for the solid state lighting phosphor as well as white light-emitting diodes.