Tetragonal polycrystalline zirconia

Yttria blends of approximately 3% are called Tetragonal Zirconia Polycrystal (TZP) and have the finest grain size. These grades exhibit the highest toughness at room temperature, because they are nearly 100% tetragonal, but this degrades severely between 200 and 500°C as these irreversible crystal transformations also cause dimensional change.