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 α-Y2Si2O7 (space group P-1) and β-Y2Si2O7 (space group C2/m) polymorphs have been investigated and shown. The significant broadening of the emission spectra recorded for the α phase compared to the one for the β phase was discussed in terms of higher number of Y3+ sites (4) present in the α phase with respect to only one Y3+ site in the case of β phase. The higher value of the luminescence decay time of β phase (11.2 ms) compared to the α phase (8.5 ms) is associated with the higher site symmetry of β-Y2Si2O7. Moreover it was found that Er3+ concentration …