The formation of ZrX (O-N-C) phase by the carbonitriding of zircon at hightemperatures

Zirconium compounds and composites as ZrO2, ZrN, ZrN-Si2N2O, etc. art of gr eat interest for application in the ceramic field due to their good thermal and mechanical properties. The carbonitriding of oxide compounds is an alt ernative method to obtain nitrogenous phases. In this work, zircon (ZrSiO4) , a natural zirconium mineral is submitted to reduction with carbon and sim ultaneous nitriding. The temperature (up to 1650 degrees C), the C/mineral ratio, and the reaction time are the main variables. The evolution of cryst alline 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 beta" zirconium oxynitride can be obtained when reaction conditio ns are the adequate ones. Volatilisation of silica occurs during reaction. (C) 2000 Elsevier Science S.A. All rights reserved.