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.