Study of carbonitriding reactions of zirconia. Synthesis of Zr(C,N,O) phases and β-type zirconium oxynitrides

Carbonitriding reactions of ZrO2 permit obtaining Zr(C,O,N) phases that belong to the pseudoternary “ZrO–ZrN–ZrC” system and/or β-type zirconium oxynitrides belonging to the ZrO2–Zr3N4 system. The Zr(C,O,N) phase has a cubic crystalline structure with ao parameter depending on the C, O and N content. The β- type oxynitride obtained was the β″-phase corresponding to the Zr7O9,5N3,0 formula with trigonal crystalline structure. The Zr(C,O,N) composition (ao between 4.600 and 4.654 Å) and relative proportions of both phases depend on the reaction temperature (between 1400 and 1650 °C) and on the carbon content of the samples (between 0 and 33%). The reaction products were studied by X-ray diffraction (XRD). Some samples were analyzed using the Rietveld method with silicon as internal standard. The crystallite sizes of the zirconium phases were also determined by XRD. Additionally, microstructure analysis of raw materials and reaction products were performed by scanning electronic microscopy (SEM).