Octahedral iron phosphate hydroxide microcrystals: Fast microwave-hydrothermal preparation, influencing factors and the shape evolution

Octahedral Fe4(PO4)3(OH)3 microcrystals have been successfully prepared by a microwave-assisted hydrothermal route at 170 °C for 20 min, employing FeCl3·6H2O and NaH2PO4·2H2O as the starting materials in the presence of proper amounts of Na2SO3 and acetic acid (HAc). The phase and morphology of the as-prepared product were characterized by means of powder X-ray diffraction (XRD), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Some factors influencing the formation of octahedral Fe4(PO4)3(OH)3 microcrystals were systematically investigated, including the reaction temperature, time, and the molar ratio of Na2SO3/HAc.

Graphical abstractOctahedral Fe4(PO4)3(OH)3 microcrystals have been successfully prepared by a microwave-assisted hydrothermal route at 170 °C for 20 min. The morphology of Fe4(PO4)3(OH)3 could be tuned by the Na2SO3/HAc molar ratio.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Fe4(PO4)3(OH)3 octahedra had been hydrothermally prepared under the microwave assistance. ► The morphology of the final product could be tuned by the original molar ratio of Na2SO3/HAc. ► Low or high temperatures were unfavorable for the formation of Fe4(PO4)3(OH)3 octahedra. ► The time-dependent shape evolution of the final product was investigated.