Densification and microstructure of a ZrO2–SiO2 glass-ceramic prepared by using mesoporous particles as raw powder

Ceramic sintering is an energy-consuming process. Reducing sintering temperature and shortening dwelling time are significant to the reduction of carbon footprint. It has been reported that utilizing mesoporous particles as raw powder for sintering is a promising strategy to achieve the above goal. The goal of this study is to verify if this strategy also works for the sintering of ZrO2–SiO2 glass-ceramics. We synthesized mesoporous particles through a micelle-assisted co-precipitation process, followed by sintering by fast hot pressing (FHP) and pressureless sintering (PS) to obtain ZrO2–SiO2 glass-ceramics. For comparison, solid particles without mesopores were synthesized by a sol-gel method and consolidated by the two sintering techniques. The densification behaviors of the two types of particles were comparatively investigated. Results showed that the mesopores collapsed at ∼850 °C during FHP due to the applied pressure, which resulted in a peak densification rate during the whole sintering process. The mesoporous particles (∼820 °C) had a lower densification starting temperature than that of the solid particles (∼910 °C). However, the mesoporous particles showed a longer densification process and a lower average densification rate than those of the solid particles. The samples sintered from mesoporous particles showed a heterogeneous microstructure, predominately consisting of ZrO2 nanocrystallites embedded in a SiO2 matrix, but in some regions ZrO2 sub-microcrystallites were connected with each other by grain boundaries, without the presence of SiO2 matrix. During PS, there was not significant differences in the densification between the mesoporous particles and the solid ones. These results demonstrate that the mesoporous particles did not show significant advantages over solid ones, in terms of the densification of ZrO2–SiO2 glass-ceramics.