In situ X-ray diffraction studies of the crystallization of VOHPO4·0.5H2O

Time resolved in situ X-ray diffraction was used to study the formation of vanadyl hydrogen phosphate hemihydrate (VOHPO4·0.5H2O) in organic media. This technique has identified a new phase at early synthesis times (less than 300 s) at a d-spacing of 7.5 and 3.1 Å. The feature at 7.5 Å shifted to 6.7 Å during the first 20 min of synthesis and this phase collapsed as VOHPO4·0.5H2O formed. Thin symmetrical platelets of <F>10 μm×10</F> μm dimensions were observed when samples were recovered after short synthesis times. Energy dispersive X-ray analysis indicated that these platelets contained vanadium and phosphorus. The platelets appeared to delaminate possibly associated with the strain generated when the d-spacing shifted from 7.5 to 6.7 Å, from which growth of the VOHPO4·0.5H2O into the familiar rosette morphology occurs. [Copyright &y& Elsevier]