engleski

p-Type and n-Type Behavior of Chromium Oxide as a Function of the Applied Potential

Thermodynamic data as well as physical and electrochemical studies demonstrate that the composition of the passivelayer on chromium depends on the potential and the electrolyte pH. The electrochemical properties of Cr2O3 electrodeswere compared with the anodic behavior of chromium in borate buffer solutions. The feasibility of the solid-phase transformationof a surface layer under anodic polarization was investigated. The conductivity type and deviation from the stoichiometriccomposition of the chromium oxide was determined in situ using the photopolarization method. Dependingon the polarization potential, stoichiometric point defects in Cr2O3 result in the p- or n-type behavior of the oxide. The formula can be expressed as CrmOn–x (or Crm+On where x > 0). Photopolarization measurements suggest that Cr2O3 behavelike a p-type semiconductor at low anodic potentials, but it shows n-type behavior at high anodic potentials. The transitionfrom p-type to n-type conductivity is a pH-dependent reversible process, occurring at potentials corresponding to thetransformation of Cr2O3 (p-type) to CrO2 (n-type) via the solid-state mechanism.

Cr2O3; borate buffer; semiconducting properties

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