Vibrational spectra and thermal dehydration of Co2P2O7·6H2O diphosphate

Raman (Ra) and infrared (ir) spectra of Co2P2O7_6H2O are interpreted using factor group analysis. No coincidences of most of Raman and infrared spectra bands confirms a centrosymmetric structure for this salt. The vibrational spectra point to a bent POP bridge angle in this compound. Thermal dehydration of Co2P2O7_6H2O in the range 25–800 8C was investigated by thermogravimetric analysis (TG and DSC), and infrared spectroscopy. According to the TG–DSC curves, the ehydration takes place in two stages. The results of the thermal analysis of the compound (heated at different temperatures) showed that, after dehydration, Co2P2O7_6H2O first decomposes in Co2P2O7_2H2O, then in an amorphous product, which crystallizes at 592 8C giving rise to the anhydrous form a-Co2P2O7. The DH enthalpy of the dehydration and phase transition of the Co2P2O7_6H2O salt has been calculated from the thermogravimetric data.