On the reported high-temperature phase transition in KH2PO4 -: Strong evidence of partial polymerization instead of a structural phase transition

X-ray diffraction and thermogravimetric analysis (TGA) were used to study the kinetic process of dehydration and the high-temperature phase transition (HTPT) at Tau(p) = 453 +/- 10 K in KH2PO4. Our results show strong evidence that the earlier reported phase transition at Tau(p) is not a structural transition of the tetragonal phase to a monoclinic high-temperature modification of KH2PO4, instead the transition is due to the formation of various polymeric intermediates, K(n)H(2)P(n)O3(n+1) during the course of dehydration to finally form (KPO3)(n) over the surface of the sample. Thus our results support Lee's suggestion (J. Phys. Chem. Solids, 1996, 57, 333) that the term HTPT should be replaced by "onset of partial polymerization" at reaction sites distributed on the surface. (C) 1997 Elsevier Science Ltd.