Effect of alkaline earth additives on the flexural strength of silicon oxycarbide-bonded silicon carbide ceramics

A series of silicon oxycarbide (SiOC)-bonded SiC ceramics were fabricated from SiC–polysiloxane–alkaline earth (AE) alkoxide mixtures at a temperature as low as 800 °C to investigate the compositional effect on the flexural strength of SiOC-bonded SiC ceramics. The addition of AE elements increased the flexural strength of SiOC-bonded SiC ceramics by 14–65% depending on the composition. The flexural strength versus the Ba/(Ba+Si) mole ratio curve had a maximum in that there was a small composition range for which an optimum flexural strength occurred. The best result, a flexural strength of >150 MPa, was obtained when the ratio was ∼0.01.