Microstructural characterization of superplastic SiO₂-doped TZP with a small amount of oxide addition

The microstructures of 5 wt% SiO₂-doped TZP, 5 wt% (SiO₂ + 2 wt% MgO)-doped TZP, and 5 wt% (SiO₂ + 2 wt% Al₂O₃)-doped TZP are characterized by high-resolution electron microscopy, energy-dispersive X-ray spectroscopy, and electron energy loss spectroscopy. An amorphous phase is formed at multiple grain junctions but not along the grain-boundary faces in these three materials. A small addition of MgO and Al₂O₃ into the SiO₂ phase results in a marked reduction in tensile ductility of SiO₂-doped TZP. This reduction seems to correlate with segregation of magnesium or aluminum ions at grain boundaries and a resultant change in the chemical bonding state.