Final Answer:
Yttria-stabilized zirconia (YSZ) is made by doping ZrO2 with yttrium, with yttrium appearing as substitutional defects on the cation sub-lattice.
Step-by-step explanation:
Yttria-stabilized zirconia (YSZ) is a crucial material in various high-temperature applications, such as solid oxide fuel cells and thermal barrier coatings. The term "yttria-stabilized" indicates the addition of yttrium oxide (Y2O3) to zirconia (ZrO2). In the ZrO2 lattice, yttrium ions replace zirconium ions in a process known as substitutional doping.
The addition of yttrium introduces extra oxygen vacancies into the lattice, promoting oxygen ion conductivity. This is particularly valuable in applications like solid oxide fuel cells, where oxygen ion transport is vital for the functioning of the cell. Yttrium's smaller size compared to zirconium allows for better stabilization of the cubic phase of ZrO2 at lower temperatures, enhancing its performance and durability.
The substitution of yttrium into the cation sub-lattice plays a key role in preventing the transformation of ZrO2 from a high-temperature stable cubic phase to a lower-temperature stable tetragonal phase. This transformation can lead to volume changes and structural instabilities, which YSZ helps mitigate, ensuring the material's reliability in extreme conditions.
Overall, the controlled introduction of yttrium through substitutional doping is essential for tailoring the properties of YSZ to meet the specific demands of various technological applications.