Semiconducting properties of thermal scales grown on a chromia-forming alloy under controlled oxygen partial pressures

• A model chromia-forming alloy was studied.
• The PEC techniques have proven to be very sensitive to minor oxide phases in scales.
• The study has revealed an unexpected number of oxide phases in thermal scales.

The present work is focused on the oxidation at 1050 °C of a model chromia-forming alloy, paying special attention to the control of the oxygen partial pressure. Taking benefit of a recently developed approach to describe and fit photocurrent energy spectra, photoelectrochemical characterizations allowed to reveal the presence, in the scale formed at low P(O2) (10−15 atm), of an unexpected high number of oxide phases. This result underlines the complexity of the scale in term of chemical composition as well as of the semiconducting types of the individual phases.