Electrochemical behaviour of niobium and niobium passive films in nitric acid solutions

Abstract

<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">Electrochemical behaviour of bare niobium and phosphoric acid anodized niobium electrodes is investigated in nitric acid solutions. Electrochemical impedance spectroscopy and polarization techniques have been used to investigate the open-circuit growth of the passive film. The stability of the anodic oxide film has been studied as a function of the formation voltage, formation current density and concentration of the ambient electrolyte. The results show that the Nb-Nb₂O₅-1M HNO₃ does not behave as a perfect dielectric. The flat band potential and donor concentration of the semiconducting anodic oxide film have been calculated from the Mott-Schottky plots.</span>