Defect structure and related properties of mayenite Ca12Al14O33

• High temperature red/ox behavior and hydration of mayenite was modeled.
• Conventional Kröger–Vink method was successfully applied.
• Mayenite enthalpy of reduction was found to be equal to 360 kJ/mol.
• Mayenite hydration enthalpy was found to be equal to − 238 kJ/mol.
• Mayenite oxygen nonstoichiometry was estimated.

For the first time, the defect structure of mayenite was developed on the basis of conventional Kröger–Vink method and successfully verified using available data on its properties such as total conductivity, hydration/dehydration and oxidation/reduction. As a consequence, equilibrium constants of the quasichemical reactions of mayenite reduction and hydration were determined as a function of temperature. This allowed estimation of Ca12Al14O33 − δ enthalpy of reduction and hydration. The former was found to be equal to 360 kJ/mol while the latter was estimated as − 238 kJ/mol. The defect structure model proposed enabled estimation of oxygen nonstoichiometry in mayenite.