A new pressureless hydrothermal method for the preparation of yttrium disilicate is presented. The obtained amorphous precursor was calcined at different temperatures to form the Y-, R-, -, and γ-phases of Y 2 Si 2 O 7 , which have been characterized by DTA, XRD, TEM, and 29 Si-MAS RMN and IR spectroscopy. It is shown that the proposed method allows the strictly controlled doping of yttrium disilicate using RE elements such as dysprosium (2.5 and 5 at. %). The luminescent properties, in terms of emission efficiency, of different polymorphs of Dy-doped Y 2 Si 2 O 7 have been investigated by fluorescence measurements at room temperature. The results indicate that the -phase doped with 2.5 at.% has the maximum efficiency. It is important to note that the efficiency of this phase is approximately 40% of that measured for the commercial phosphor Eu-Y 2 O 3 .