Grain-boundary structure and microstructure development mechanism in 2–8 mol% yttria-stabilized zirconia polycrystals

Microstructural developments during sintering in 2 and 3 mol% Y2O3-stabilized tetragonal zirconia polycrystals (2Y- and 3Y-TZPs) and 8 mol% Y2O3-stabilized cubic zirconia (8Y-CSZ) were systematically investigated in the sintering temperature range of 1100–1500 °C. Above 1200 °C, grain growth in 8Y-CSZ was much faster than that in 2Y- and 3Y-TZPs. In the grain-boundary faces in these specimens, amorphous layers did not exist; however, Y3+ ions segregated at the grain boundaries over a width of ∼10 nm. The amount of segregated Y3+ ions in 8Y-CSZ was significantly less than in 2Y- and 3Y-TZPs. This indicates that an increase in segregated Y3+ ions retards grain growth. Therefore, grain growth behavior during sintering can be reasonably explained by the solute-drag mechanism of Y3+ ions segregating along the grain boundary. The segregation of Y3+ ions, which directly affects grain growth, is closely related to the driving force for grain-boundary segregation-induced phase transformation (GBSIPT).