Abstract

A procedure for the synthesis of high acicular and uniform goethite particles based on a modified-carbonate route is reported. It essentially consists of the oxidation–precipitation of iron sulfate solutions through a two-oxidation process, which involves the formation of primary particles and their subsequent growth. XRD, TEM, colour evolution and pH monitoring have been used to determine the mechanism responsible for the formation of goethite particles with well-controlled morphology. Single-phase goethite particles are formed from initial suspensions with OH/Fe equivalent ratios from 0.05 to 0.35, which determine the supersaturation level of the solution and consequently, the length of the particles. The best conditions to prepare uniform goethite particles of 250 nm in length and high axial ratio (8), adequate as high-density audio/video media precursors, have been established.