Tunable Red-Yellow Coloration of .BETA.-FeOOH Pigments by Coating and Controlling Morphology

In this work, we studied the morphology, phase transition, and coloration of beta-FeOOH using a core-shell structure. First, rod type beta-FeOOH was prepared by hydrolysis of [Fe3+]/[Cl-] as a raw material. Especially, various yellow values of beta-FeOOH were tuned using the length and coating approaches. We found that when the length was increased, the yellow value also increased. High quality red coloration was obtained after heat treatment of the core-shell beta-FeOOH structure. Details of the coloration and phase structure of beta-FeOOH were characterized by UV-vis, CIE Lab color parameter measurements, TEM (transmission electron microscopy), SEM (scanning electron microscopy), and XRD (powder X-ray diffraction).