YSZ stands for yttria-stabilized zirconia, which is a ceramic material commonly used in high-temperature applications. The addition of yttria to zirconia helps to stabilize the cubic phase, which is the most stable and desired phase for many applications.
The cubic phase of zirconia has several desirable properties, including high strength and toughness, resistance to thermal shock, and good electrical and mechanical properties. Stabilizing zirconia in this phase allows it to be used in a wide range of applications, such as in solid oxide fuel cells, thermal barrier coatings, and ceramic knives.
Yttria has a similar atomic size and charge to zirconia, which allows it to replace some of the zirconia atoms in the crystal lattice. This disrupts the formation of the tetragonal and monoclinic phases, which are less stable, and promotes the formation of the cubic phase.
The amount of yttria added, the temperature and time of sintering, and the cooling rate can all affect the stabilization of zirconia in the cubic phase. Higher yttria content and longer sintering times tend to result in a higher proportion of cubic phase, while rapid cooling can cause the formation of other phases.
One limitation is that the cubic phase is only stable at high temperatures, typically above 1200°C. This can make the manufacturing process more challenging and expensive. Additionally, zirconia can undergo phase transformations under certain conditions, such as mechanical stress or exposure to water, which can affect the stability of the cubic phase.