Synthesis, characterisation and optical properties of nanocrystalline Y2O3-Eu(3+)dispersed in a silica matrix by a deposition-precipitation method

A Eu3+-doped-yttria-silica nanocomposite was synthesized through a deposition-precipitation technique. Yttria nanocrystalline particles with a mean size of 12 nm, dispersed in an amorphous silica matrix, were evidenced by XRD and TEM in a sample treated at 900 degreesC. The nanoparticles are coated with an amorphous layer visible in the HRTEM micrographs; this amorphous layer is likely to interact with the silica matrix through Si-O-Y bonds, which is consistent with Si-29 NMR MAS results. The nanocomposite treated at 1000 degreesC partially evolves to give an alpha-Y2Si2O7 crystalline phase. The luminescence spectra of the nanocomposites indicate that the sites in which the Eu3+ ions are accommodated are disordered. On the other hand, the decay times of the D-5(0) emission are rather long in the present nanocomposites studied herein, indicating that multiphonon relaxation is not effective in quenching the luminescence. The reduced coupling to OH vibrations in the materials under investigation could be ascribed to the presence of the amorphous layer coating the nanoparticles and effectively shielding the Eu3+ ion from the silanol groups.