Synthesis of novel green phosphate pigments in imitation of natural ores

As novel green pigment, various sodium iron phosphates, Na4Fe7(PO4)6, NaFe4(PO4)3, and Fe3(PO4)2, imitated with Xenophillite and Vivianite, were synthesized using a hydrothermal process. The obtained powders were estimated with X-ray diffraction (XRD), Infrared (IR) spectra, ultraviolet-visible (UV-vis) reflectance spectra, and L*a*b* color space. The hydrothermal temperature and time, volume of water, phosphorus resource were studied in this process. All samples prepared in this work were dark green powders. The weak peaks of Na4Fe7(PO4)6 and Fe3(PO4)2 were observed in XRD patterns of all samples. Hydrothermal treatment of a long duration produced high greenish powders. The large volume of water used improved the greenish and bluish colors of the phosphate powders.