Electrochemical and optical characterization of the anodic growth of antimony oxide films.

O. E. LINAREZ PÉREZ; M. A. PÉREZ; M. LÓPEZ TEIJELO

Sao Pedro, Estado de Sao Pablo, Brazil.

Congreso; 54th Annual Meeting of the International Society of Electrochemistry; 2003

Antimony is used as an alloying additive in lead alloys for grids in lead-acid batteries. It has also received some attention due to the use of antimony oxide as a photoconductor material, although its duration is low due to corrosion. Previous studies on the formation and properties of antimony oxide in different solutions have been limited to low potentials. Also, the dissolution behaviour of the anodic film formed in phosphate solutions has been studied by impedance measurements.In this work the anodic growth of antimony oxide films electroformed under potentiodynamic or galvanostatic conditions as well as their stability in the formation electrolyte were studied. Antimony oxide films of different thickness were grown potentiodynamically or galvanostatically up to different potential values in solutions of different concentration and pH. Ellipsometry in situ was used for monitoring the anodic growth of the oxide films as well as at the open circuit potential in the formation electrolyte for studying the dissolution process. In addition, EIS experiments were performed in order to characterize the electrical properties of the electroformed films.The electrochemical results indicate that the anodic behaviour is dependent on the anion of the electrolyte. The j/E potentiodynamic profiles show three main anodic current peaks which are attributed to the formation of a layer containing Sb(III) species through a complex mechanism in three stages [1]. After this region, the current density reaches an approximately constant value and, depending on the electrolyte nature, increases again up to define another potential region of stationary current at potentials exceeding ca. 3-4 V, which are associated with the anodic growth of the antimony oxide layer. Potentiodynamic data indicate that at high potentials the film growth occurs through a mechanism of ionic migration under a high field. From experiments applying combined repetitive sweeps with potential holdings and simulations of the current/potential curves for high-field anodic growth, it can be deduced that the anodic films are porous.The ellipsometric data obtained during the anodic growth allow us to obtain the optical constants of the layers as well as the film thickness from which the growing field can be characterized. Impedance data show the existence of contributions of the porous oxide/solution interface [2].References[1] D. Pavlov, M. Bojinov, T. Laitinen, G. Sundholm, Electrochim. Acta 36 (1991) 2087.[2] J. H. W. de Witt, H. J. W. Lenderik, Electrochim. Acta 41 (1996) 1111.Acknowledgements: This research has been supported by CONICET, Agencia Córdoba Ciencia S.E., SECYT-UNC and Fundación Antorchas.