Zirconia ceramics consolidated by oscillatory pressure sintering and subsequent carburization

Abstract

We proposed a novel method consisting in the combination of oscillatory pressure sintering (OPS) followed by carburization in the vacuum, to prepare zirconia ceramics with high fracture strength and Weibull modulus. In this study, the zirconia particles were densified by an oscillatory pressure ranging from 27.5 to 32.5 MPa at 1450 °C, and then were carburized in the vacuum at 1300 °C. The result showed that the oscillatory pressure achieved several densification mechanisms, such as rearrangement of particles, plastic deformation of grains and sliding of grain boundaries. Consequently, the OPS specimen exhibited an increase in flexural strength from 998 MPa to 1556 MPa, and grain size reduction from 460 nm to 283 nm. The subsequent carburization of OPS zirconia induced high concentration of oxygen ion vacancies, and then high content and stability of the tetragonal phase. Thus, the carburized zirconia exhibited excellent comprehensive behaviors, demonstrating a flexural strength of 1646 MPa, fracture toughness of 8.8 MPa m1/2 and Weibull modulus of 25.8. The combination of OPS and consequent carburization in the vacuum is considered as an effective technique for preparing high-quality zirconia ceramics.