Thermal structure characteristics of disorder goethite and their electrical properties determined by impedance spectroscopy

Iron (III) oxy hydroxides were synthesized from solutions of iron (III) sulfate and sodium hydroxide at room temperature followed by treatments with steam in KOH at different times. Oxy hydroxides were characterized by thermal analysis, IR spectroscopy, X-ray diffraction and electrical measurements. Iron oxy hydroxides with different degree of crystallinity were obtained from different treatment times with steam whose results were related by the above techniques. The iron (III) oxide obtained maintains his defective structure up to a temperature between 575 to 725 Centigrade. Electrical characteristics of the oxides are shown and their relationships to the crystallinity and the silicon content. In order to characterize the electrical properties the technique of impedance spectroscopy was used. Equivalent circuits were used to facilitate the calculation of electrical parameters. (Author)