The role of the SnO2 interphase in an alumina/glass composite: a fractographic study

The role of tin dioxide (SnO₂) interphase for the alumina/glass composite system was investigated using fractography. Alumina (Al₂O₃) and glass form a strong chemical bond which is undesirable for toughness in a ceramic matrix composite. SnO₂ interphase was incorporated to prevent this strong bond between alumina and glass. SnO₂ was deposited on Al₂O₃ substrates via chemical vapour deposition and bonded with glass. The role of the interphase was then studied by characterizing the fracture surfaces of the bend test and special composite disc samples loaded in diametral compression. Bend tests results showed that the SnO₂ interphase and/or the SnO₂/Al₂O₃ interface acted as a plane of weakness. Secondary cracking at 90° to the major crack direction was observed along this plane of weakness, which appears to be in accord with the Cook and Gordon model. Crack deflection and secondary cracking were also observed in the SnO₂ region of the compression samples. These results indicate the suitability of SnO₂ interphase for the alumina/glass composite system.