Tetragonal polycrystalline zirconia
blends of approximately 3% are called either tetragonal polycrystalline zirconia or tetragonal zirconia polycrystal 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.
