Kinetic process of dehydration at fusion temperature and the high-temperature phase transition in KH2PO4

Abstract

X-ray diffraction and Raman spectroscopy analysis were used to study the kinetic process of dehydration and the high-temperature phase transition (HTPT) in KH2PO4. The results show strong evidence that KH2PO4 presented two phase transitions at about Ttr=453K and 483K. The new Raman bands, which were observed in the KDP (phase (Ia) and phase (Ib)) spectra (at 128, 152, 372, 437, 540, 904, 926, 966, 1100, 1156 and 1171cm−1), did not correlate to any of the highly intense peaks present in KPO3 (383, 671, and 1139cm−1), K2H2P2O7 (705 and 1041cm−1), and the KnH2PnO3n+l (n≫l) polymer (294cm−1) spectra, indicating that a number of structural changes took place. Accordingly, the results presented in the current work corroborate the findings of former studies attributing the phenomena at high temperature in KDP to structural phase transition rather than thermal decomposition.