A new neodymium-sodium cyclotriphosphate Na3Nd3(P3O9)(4). 13H(2)O has been prepared for the first time, using a classical method of aqueous chemistry and characterized by X-Ray diffraction, thermogravimetric analysis and infrared spectroscopy which shows the characteristic bands of cyclo-triphosphates as the triplet in the 1340-1293-1257 cm(-1) area, The results of differential thermal analysis, X-Bay powder diffraction and IR, spectra of the compound heated at different temperatures showed that, after dehydration, Na3Nd3(P3O9)(4). 13H(2)O decomposes into an amorphous compound, then it crystallizes at 926 K in order to give the polyphosphate NaNd(PO3)(4), that decomposes at 1160 K to give the Nd(PO3)(3).