Crystallization Behavior of Novel Silicon Boron Oxycarbide Glasses

Homogeneous silicon boron oxycarbide (Si‐B‐O‐C) glasses based on SiO x C 4– x and BO y C 3– y mixed environments were obtained by pyrolysis under inert atmosphere of sol–gel‐derived precursors. Their high‐temperature structural evolution from 1000° to 1500°C was followed using XRD, 29 Si and 11 B MAS NMR, and chemical analysis and compared with the behavior of the parent boron‐free Si‐O‐C glasses. The XRD study revealed that, for the Si‐O‐C and the Si‐B‐O‐C systems, high‐temperature annealing led to the crystallization of nanosized β‐SiC into an amorphous SiO 2 ‐based matrix. NMR analysis suggested that the β‐SiC crystallization occurred with a consumption of the mixed silicon and boron oxycarbide units. Finally, by comparing the behavior of the Si‐O‐C and Si‐B‐O‐C glasses, it was shown that the presence of boron increased the crystallization kinetics of β‐SiC.