Synthesis and characterization of alpha-hopeite, Zn-3(Po-4)(2)center dot 4H(2)O

Orthorhombic alpha-Zn-3(PO4)(2). 4H(2)O, alpha-hopeite, was synthesized fro m an aqueous solution of zinc acetate and orthophosphoric acid. The synthes is from these starting materials yielded best results with respect to purit y and crystallinity. Structural characteristics of the compound were invest igated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scan ning electron microscopy (SEM), and thermogravimetric/differential thermal analysis (TG/DTA). Supplemental data came from surface area, particle size distribution, and density measurements. The obtained compound proved to be highly crystalline and stoichiometric. Dehydration of alpha-hopeite is acco mpanied by at least two endothermic effects and already starts at temperatu res <373 K. This observation has important implications for the technical z inc phosphate coating process. The dehydration behavior can be explained by results from low-temperature diffuse reflectance IR spectroscopy (DRIFT). (C) 2000 Elsevier Science Ltd.