Changing the calcination temperature to tune the microstructure and polishing properties of ceria octahedrons

Ceria octahedrons with different microstructure and surface characteristics were prepared by calcining an octahedral CeO₂ precursor self-assembled from spherical primary nanocrystals of about 5 nm at 500-900 °C. Structural characterization revealed that with the calcination temperature increasing from 500 to 700 °C, the products maintained a hierarchical structure and primary nanocrystals changed from spherical to octahedral particles. Significant fusion occurred between the primary nanocrystals and the surface of the octahedrons became smooth at the calcination temperature of 800 °C. Single crystal CeO₂ octahedrons were formed when the calcination temperature reached 900 °C. The change in microstructure induced by elevated calcination temperature led to increased mechanical hardness and decreased surface chemical activity (specific surface area and surface Ce³⁺ concentration) of the octahedrons, which had an impact on their polishing performance. The polishing experiments on K9 glass showed that the polishing rate first increased and then decreased with the increment of calcination temperature, indicating that in addition to the mechanical hardness, the surface chemical activity of the octahedrons is also important for material removal. Owing to the best matching of chemical activity and mechanical hardness, CeO₂ octahedrons calcinated at 700 °C exhibited the highest polishing rate and the best surface quality for K9 glass.