ANODIC FORMATION AND PROPERTIES OF COPPER OXIDES ON Cu,Zn(α)-ALLOYS WITH STRUCTUTE-DISORDERED SURFACE LAYER

Abstract

The paper is aimed to reveal an influence of vacancy defectiveness of the alloys surface layer on anodic oxide formation and electronic properties of oxide nanofilms. The monitored vacancy defectiveness of surface layer in Cu-Zn alloys (up to 30 at.% of Zn) was generated in the course of potentiostatic selective dissolution (SD) in aqua deaerated solution 0.01 M HCl + 0.09 M KCl. It was revealed that the SD is limited by interdiffusion of alloy’s components in the surface layer. The diffusion coefficient and vacancy concentration (or vacancy defectiveness) in the surface layer noticeably increase with the potential of SD. Atomic force microscopy and impedance measurements prove a slight increase of capacity and roughness at the alloy/solution boundary after the selective dissolution. The anodic oxide formation on the alloys with a certain vacancy defectiveness was examined by linear voltamperometry and chronoamperometry in aqua deaerated solution 0.1 M KOH. The potentials of formation of Cu(I) and Cu(II) oxides do not depend on the vacancy concentration in the alloy’s surface layer. Coulometric measurements show a slight decrease of current efficiency of oxide formation with the vacancy concentration. The  electronic properties of copper oxides on these alloys were determined by Mott-Schottky method. It was shown that the flat band potentials of Cu(I) and Cu(II) oxides do not change at transition from copper to alloys with different concentration of zinc and superequilibrium vacancies. The concentration of acceptor defects in Cu(I) and Cu(II) oxides significantly increases with the vacancy defectiveness in the surface layer of Cu-Zn alloys.

ACKNOWLEDGEMENTS

The work was supported by the Ministry of Education of the Russian Federation in the framework of Goszadaniya universities in 2014-2016 gg., 675 project.