Hydrothermal preparation of goethite crystals

Abstract

The precipitation of goethite particles by a hydrothermal procedure is described. The reaction involves the oxidation of ferrous ion solutions with hydroxylamine salts at 85 °C.

The phase purity of the oxide is discussed as a function of the solution composition, and in particular of the pH and of the different anions. Scanning electron microscope examinations show that goethite particles are acicular crystals with a rather narrow size distribution. The crystals show prismatic shape and appear to be elongated in the [001] crystallographic direction. The attribution of {110} form to the side faces of the prisms is proposed.