IMPORTANCE OF GRAIN-BOUNDARY CHEMISTRY ON THE HIGH-TEMPERATURE PLASTIC-FLOW IN OXIDE CERAMICS

High-temperature plastic flow associated with grain boundary sliding i n fine grained oxides is often very sensitive to a small addition of d opant cation. The dopant effect is examined in high-purity, fine-grain ed Al2O3 and SiO2-containing tetragonal zirconia polycrystal (TZP). Hi gh-temperature flow stress and tensile ductility are dependent on the type of dopant. High-resolution TEM-EDS, TEM-EELS and X-ray photoelect ron spectroscopy (XPS) analyses reveal that the dopant cations segrega te in grain boundaries and that the grain boundary chemical bonding st ate changes by the segregation. Grain boundary sliding must be affecte d seriously by the dopant segregation through the change in chemical b onding state in grain boundaries. (C) 1997 Elsevier Science S.A.