Synthesis and Photoluminescence of Tetravalent Cerium-Doped Alkaline-Earth-Metal Tungstate Phosphors by a Co-precipitation Method

A series of tetravalent cerium ion-doped alkaline-earth-metal tungstate phosphors were prepared by a co-precipitation method with a mixture of ammonium bicarbonate and aqueous ammonia as the precipitating agent. X-ray diffraction, scanning electron microscopy, and photoluminescence were used to characterize the structure, morphology, and luminescent properties of the phosphors. The synthesized cerium-doped tungstate phosphors have a scheelite structure with a pure phase. The scanning electron microscope images show that the grain sizes are in the range from 1.0 to 3.0 mu m. Photoluminescence spectra indicate blue emission around 440 nm and the optimized concentrations of tetravalent cerium were 3.0, 2.0, and 3.0 in calcium tungstate, strontium tungstate, and barium tungstate for the highest emission intensities at 365 nm excitation. The Commission Internationale De L'E'clairage chromaticity coordinates of cerium-doped tungstate phosphors, that is, x = 0.14, y = 0.14, exhibit pure blue emission and the synthesized phosphors are promising materials for visual display and solid-state lighting applications.