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

Abstract

This paper describes the preparation, optical absorption and photoluminescent properties of (1 − x)CaWO 4: 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)CaWO 4: 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 CaWO 4 host to them. The energy transfer from WO 4 2− groups to Ln(III) ions is particularly effective for 0.67CaWO 4:0.33Eu(III) or 0.95CaWO 4:0.05Tb(III) incorporated into SiO 2 xerogel. The high emission and easy preparation of these systems make them potential candidates for use as luminescent materials.