Importance of grain boundary chemistry on the high-temperature plastic flow in oxide ceramics

High-temperature plastic flow associated with grain boundary sliding in fine grained oxides is often very sensitive to a small addition of dopant cation. The dopant effect is examined in high-purity, fine-grained Al2O3 and SiO2-containing tetragonal zirconia polycrystal (TZP). High-temperature flow stress and tensile ductility are dependent on the type of dopant. High-resolution TEM-EDS, TEM-EELS and X-ray photoelectron spectroscopy (XPS) analyses reveal that the dopant cations segregate in grain boundaries and that the grain boundary chemical bonding state changes by the segregation. Grain boundary sliding must be affected seriously by the dopant segregation through the change in chemical bonding state in grain boundaries.