Low temperature preparation of Ce-TZP/Ba hexaaluminate composites

Abstract

Composites consisting of Ce-TZP matrix and in-situ grown particles of barium hexaaluminate (BaAl₁₂O₁₉) as the second phase were prepared. To lower the sintering temperature and improve the microstructure of the composites, starting materials of two types of the second phase were used: mixed powders of BaCO₃ and α-Al₂O₃, and amorphous precursor powder. When the composites were prepared using the mixed powder of BaCO₃ and larger α-Al₂O₃ (3.0 µm) particles, aggregations of in-situ formed BaAl₁₂O₁₉ particles were observed in the Ce-TZP matrix. Although the formation temperature of BaAl₁₂O₁₉ decreased with decreasing average size of α-Al₂O₃ particles, full dense composites were unobtainable, even at the sintering temperature of 1400°C. To lower the formation temperature of the second phase further, amorphous precursor powder of BaAl₁₂O₁₉ was prepared using coprecipitation method. The composite prepared using the amorphous precursor powder was sufficiently densified at 1400°C. The BaAl₁₂O₁₉ particles formed in the composite were finer than those prepared using the mixed powder of BaCO₃ and α-Al₂O₃.