Energy transfer in calcium tungstate doped with Eu(III) or Tb(III) ions incorporated into silica xerogel

This paper describes the preparation, optical absorption and photoluminescent properties of (1 − x)CaWO4:xLn(III) (where Ln = Eu or Tb) incorporated into silica xerogel. The photoluminescence behaviour of the inorganic material in rigid matrix was studied by means of luminescence spectroscopy. The excitation spectra of the system (1 − x)CaWO4:xLn(III) show an intense broad band with a maximum at about 240 nm, which is attributed to O → W ligand-metal charge transfer (LMCT) inside the tungstate group. Moreover, lanthanide ions exhibit their characteristic emission in the material owing to an energy transfer from CaWO4 host to them. The energy transfer from WO42− groups to Ln(III) ions is particularly effective for 0.67CaWO4:0.33Eu(III) or 0.95CaWO4:0.05Tb(III) incorporated into SiO2 xerogel. The high emission and easy preparation of these systems make them potential candidates for use as luminescent materials.