Microstructural evolution in 8mol% Y2O3-stabilized cubic zirconia (8YSCZ) with SiO2 addition

Abstract

The densification, grain-growth and microstructural evolution of high-purity 8 mol% yttria-stabilized cubic zirconia (8YSCZ) with SiO 2 addition were investigated. The addition of 1 wt.% SiO 2 enhanced the sinterability of 8YSCZ, compared with 8YSCZ without additive. In particular, doped 8YSCZ achieved a density of 99% of its theoretical value at 1300 °C, while undoped 8YSCZ reached the same value at 1400 °C. The densification mechanism associated with this process is generally considered attributable to liquid phase sintering. For grain-growth measurements, the specimens sintered at 1400 °C were annealed at 1400, 1500 and 1600 °C for 10, 30 and 66 h. It was seen that grain-growth rate could also be controlled by the deliberate addition of 1 wt.% SiO 2 . A grain-growth exponent of 2 and an activation energy for grain-growth of 298 kJ/mol were obtained for undoped 8YSCZ. The SiO 2 -containing specimens had a grain-growth exponent of 3 and an activation energy of 382 kJ/mol. The slow grain-growth in doped 8YSCZ is due to the lower grain boundary mobility and energy, which result from solute segregation in the grain boundary and its drag in doped 8YSCZ but not in undoped 8YSCZ. The drag effect arises from any preferred segregation of impurities either to or from grain boundary area because of size and charge differences. SiO 2 is expected to segregate to grain boundaries. This segregation layer is believed to hinder grain-growth by resulting in limiting matter transfer along the grain boundary.