Preparation of Zirconia Ceramics with High Density and Fine Grains by Oscillatory Pressure Sintering

Abstract

To fulfill the demands of ceramic components with high strength, high toughness and high reliability in key projects, a novel oscillatory pressure sintering (OPS) method was proposed in this study. With this new method, zirconia ceramics with high relative density, fine grains, high fracture strength, and excellent reliability, were prepared. As a comparison, zirconia ceramics were sintered by pressure-less sintering (PS) method and hot pressing (HP) method at same temperature. SEM analysis shows that the oscillatory pressure inhibits the rapid grain growth of zirconia at high temperature. Statistic results indicate that the OPS zirconia presents fine grain size at 251 nm, while the average sizes of PS and HP zirconia are 451 and 298 nm, respectively. In addition, the oscillatory pressure induces plastic deformation of grains and sliding of grain boundaries, facilitating elimination of closed pores at grain boundaries. As a result, the relative density of OPS zirconia reaches approximately 99.7%. Due to the refinement of grains and the increase in relative density, the OPS zirconia presents an increase from 1003 MPa to 1572 MPa in flexural strength, and an increase from 13 to 32 in Weibull modulus. Furthermore, its resistance to low temperature degradation is also improved because of the 208 无 机 材 料 学 报 第 31卷 microstructure evolution.