Thermo-Raman studies on dehydration of Na3PO4·12H2O

In this work, dehydration of Na3PO4·12H2O has been studied dynamically in detail by thermo-Raman spectroscopy. The dehydration was observed in the temperature range from 30 to 200°C. Spectral variation could distinguish six characteristic spectra of different hydrated species. The thermo-Raman intensity for the stretching bands of H2O showed four distinct steps of dehydration with Na3PO4·12H2O, Na3PO4·8H2O, Na3PO4·7H2O, Na3PO4·6H2O and Na3PO4·0.5H2O as the compositional species. The differential thermo-Raman intensity thermogram indicated the possibility of the existence of a new hydrated intermediate species Na3PO4·4H2O during the dehydration. The first four steps of dehydration occurred below 84°C and the last step of loosing 0.5 H2O could not be detected. The results of TG measurement showed only two stages of dehydration.