The structural evolutions and enhanced thermal stability of Al cation-modified silicon oxycarbide ceramics

Al-doped-SiOC ceramics were fabricated via condensation polymerization and then pyrolysis of preceramic precursor in this study. The Al cation induced the formation of mullite, SiO 2 and graphitic carbon. Results showed that the incorporation of Al element enhanced the thermal stability of SiOC ceramics under Ar atmosphere via suppressing carbothermal reduction. This was consistent with the observation from Raman spectra by curve-fitting according to the D-to-G peak intensity ratio. In addition, the thermal stability of the SiAlOC ceramics under air atmosphere was also investigated. The formation of the mullite phase under the air atmosphere indicated that the SiAlOC ceramics possessed better oxidation resistance properties than the pure SiOC ceramics. This work provides a new guide to fabricating metal-modified SiOC ceramics with desired structures. Graphical Abstract The introducing Al element greatly enhanced the thermal stability of SiOC ceramics via restraining in-situ formation of SiC. The structural evolutions of Al cation-modified-SiOC ceramics both in argon and air atmospheres were investigated systematically.