Crystallisation of VOHPO4·0.5H2O in the presence of a surfactant Original Research Article

The formation of vanadyl hydrogen phosphate hemihydrate (VOHPO4·0.5H2O) by progressive attachment of phosphorous to a vanadium oxide lamellar phase in the presence of cetyltrimethylammonium bromide (CTAB) is described. Evidence from nuclear magnetic resonance (NMR), XPS, X-ray diffraction (XRD) and scanning electron microscopy (SEM) is presented for the initial formation of a vanadium oxide lamellar structure with no long-range order to which phosphate is then progressively attached. Phosphate attachment leads to lamellar collapse with the resultant formation of the hemihydrate phase, VOHPO4·0.5H2O.