The synthesis of crystalline y-Y2Si2O7 has been achieved at a temperature as low as 365degreesC. This has been accomplished by following a hydrothermal method and using a layered clay as silicon source, whose structure-directing character facilitates the nucleation process. The structural characterization of the y-Y2Si2O7 polymorph is conducted with special emphasis on the MAS-NMR spectrum. Extending this finding to other binary silicate compounds allows revising the phase diagrams of these systems in the low-temperature range.