The formation of ZrX (O–N–C) phase by the carbonitriding of zircon at high temperatures

Zirconium compounds and composites as ZrO2, ZrN, ZrN–Si2N2O, etc. are of great interest for application in the ceramic field due to their good thermal and mechanical properties. The carbonitriding of oxide compounds is an alternative method to obtain nitrogenous phases. In this work, zircon (ZrSiO4), a natural zirconium mineral is submitted to reduction with carbon and simultaneous nitriding. The temperature (up to 1650°C), the C/mineral ratio, and the reaction time are the main variables. The evolution of crystalline phases during reaction is followed using XRD, weight loss and SEM. A cubic solid solution phase appears: (ZrX with X=O, C, N). Also, monoclinic ZrO2 and β′′ zirconium oxynitride can be obtained when reaction conditions are the adequate ones. Volatilisation of silica occurs during reaction.