Spectroscopic and structural properties of polycrystalline Y2Si2O7 doped with Er3+

Powders of yttrium disilicate (Y2Si2O7) doped with Er3+ have been prepared by the sol-gel method. The structure of the obtained powders has been determined. Room temperature emission spectra have been recorded and excited state decay profiles have been analyzed. Differences between the spectroscopic properties of Er3+ in monoclinic alpha-Y2Si2O7 (space group P-1) and beta-Y2Si2O7 (space group C2/m) polymorphs have been investigated and shown. The significant broadening of the emission spectra recorded for the alpha phase compared to the one for the beta phase was discussed in terms of higher number of Y3+ sites (4) present in the alpha phase with respect to only one Y3+ site in the case of beta phase. The higher value of the luminescence decay time of beta phase (11.2 ms) compared to the alpha phase (8.5 ms) is associated with the higher site symmetry of beta-Y2Si2O7. Moreover it was found that Er3+ concentration affects the shape of the I-4(13/2) -> I-4(15/2) emission band. It results in changes of the relative emission intensities of peaks localized at 1527 nm and 1532 nm; this indicates changes of the Y3+ sites occupation on increasing the Er3+ concentration. The luminescence lifetime was observed to decrease with the increase of Er3+ concentration. The spectroscopic results have been compared with the ones relative to thin films of Y2Si2O7:Er3+ with a similar composition. The lower value of the luminescence decay time observed for thin films compared to the powder of alpha phase was explained with the changes of the particles packing resulting in the change of the effective refractive index.